Operating Characteristic Curve (operating + characteristic_curve)

Distribution by Scientific Domains
Distribution within Medical Sciences

Kinds of Operating Characteristic Curve

  • receiver operating characteristic curve

  • Terms modified by Operating Characteristic Curve

  • operating characteristic curve analysis

  • Selected Abstracts

    Comparing the Areas Under Two Correlated ROC Curves: Parametric and Non-Parametric Approaches

    Katy Molodianovitch
    Abstract In order to compare the discriminatory effectiveness of two diagnostic markers the equality of the areas under the respective Receiver Operating Characteristic Curves is commonly tested. A non-parametric test based on the Mann-Whitney statistic is generally used. Weiand et al. (1989) present a parametric test based on normal distributional assumptions. We extend this test using the Box-Cox power family of transformations to non-normal situations. These three test procedures are compared in terms of significance level and power by means of a large simulation study. Overall we find that transforming to normality is to be preferred. An example of two pancreatic cancer serum biomarkers is used to illustrate the methodology. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Modelling species distributions in Britain: a hierarchical integration of climate and land-cover data

    ECOGRAPHY, Issue 3 2004
    Richard G. Pearson
    A modelling framework for studying the combined effects of climate and land-cover changes on the distribution of species is presented. The model integrates land-cover data into a correlative bioclimatic model in a scale-dependent hierarchical manner, whereby Artificial Neural Networks are used to characterise species' climatic requirements at the European scale and land-cover requirements at the British scale. The model has been tested against an alternative non-hierarchical approach and has been applied to four plant species in Britain: Rhynchospora alba, Erica tetralix, Salix herbacea and Geranium sylvaticum. Predictive performance has been evaluated using Cohen's Kappa statistic and the area under the Receiver Operating Characteristic curve, and a novel approach to identifying thresholds of occurrence which utilises three levels of confidence has been applied. Results demonstrate reasonable to good predictive performance for each species, with the main patterns of distribution simulated at both 10 km and 1 km resolutions. The incorporation of land-cover data was found to significantly improve purely climate-driven predictions for R. alba and E. tetralix, enabling regions with suitable climate but unsuitable land-cover to be identified. The study thus provides an insight into the roles of climate and land-cover as determinants of species' distributions and it is demonstrated that the modelling approach presented can provide a useful framework for making predictions of distributions under scenarios of changing climate and land-cover type. The paper confirms the potential utility of multi-scale approaches for understanding environmental limitations to species' distributions, and demonstrates that the search for environmental correlates with species' distributions must be addressed at an appropriate spatial scale. Our study contributes to the mounting evidence that hierarchical schemes are characteristic of ecological systems. [source]

    Delivering the goods: The importance of screening accuracy for effective community intervention and prevention

    Edmond D. Shenassa
    The utility and feasibility of community intervention and prevention programs depend greatly on the accuracy by which programs' participants are screened from among community dwellers. This is because indiscriminate application of the program to the entire community benefits only a few, while it can even harm the many others. It is therefore necessary to define and screen a target population so the program can be delivered exclusively to them. Consequently, screening accuracy has implications for the plan, design, and evaluation of community-based programs. In this manuscript indices of screening accuracy are discussed in the context of screening for substance use, and depression. Receiver Operating Characteristic curves, measurement error, as well as design and evaluation of community programs are also discussed in the context of screening accuracy. © 2002 John Wiley & Sons, Inc. [source]

    Screening Trauma Patients With the Alcohol Use Disorders Identification Test and Biomarkers of Alcohol Use

    ALCOHOLISM, Issue 6 2009
    Tim Neumann
    Background:, Alcohol screening and brief interventions have been shown to reduce alcohol-related morbidity in injured patients. Use of self-report questionnaires such as the Alcohol Use Disorder Identification Test (AUDIT) is recommended as the optimum screening method. We hypothesized that the accuracy of screening is enhanced by combined use of the AUDIT and biomarkers of alcohol use in injured patients. Methods:, The study was conducted in the emergency department of a large, urban, university hospital. Patients were evaluated with the AUDIT, and blood sampled to determine carbohydrate-deficient transferrin, gamma-glutamyl-transferase, and mean corpuscular volume. Alcohol problems were defined as presence of ICD-10 criteria for dependence or harmful use, or high-risk drinking according to World Health Organization criteria (weekly intake >420 g in males, >280 g in females). Screening accuracy was determined using Receiver Operating Characteristic curves. Results:, There were 787 males and 446 females in the study. Median age was 33 years. The accuracy of the AUDIT was good to excellent, whereas all biomarkers performed only fairly to poorly in males, and even worse in females. At a specificity >0.80, sensitivity for all biomarkers was <0.43, whereas sensitivity for the AUDIT was 0.76 for males and 0.81 for females. The addition of biomarkers added little additional discriminatory information compared to use of the AUDIT alone. Conclusions:, Screening properties of the AUDIT are superior to %CDT, MCV, and GGT for detection of alcohol problems in injured patients and are not clinically significantly enhanced by the use of biomarkers. [source]

    An Independent Evaluation of Four Quantitative Emergency Department Crowding Scales

    Spencer S. Jones MStat
    Background Emergency department (ED) overcrowding has become a frequent topic of investigation. Despite a significant body of research, there is no standard definition or measurement of ED crowding. Four quantitative scales for ED crowding have been proposed in the literature: the Real-time Emergency Analysis of Demand Indicators (READI), the Emergency Department Work Index (EDWIN), the National Emergency Department Overcrowding Study (NEDOCS) scale, and the Emergency Department Crowding Scale (EDCS). These four scales have yet to be independently evaluated and compared. Objectives The goals of this study were to formally compare four existing quantitative ED crowding scales by measuring their ability to detect instances of perceived ED crowding and to determine whether any of these scales provide a generalizable solution for measuring ED crowding. Methods Data were collected at two-hour intervals over 135 consecutive sampling instances. Physician and nurse agreement was assessed using weighted , statistics. The crowding scales were compared via correlation statistics and their ability to predict perceived instances of ED crowding. Sensitivity, specificity, and positive predictive values were calculated at site-specific cut points and at the recommended thresholds. Results All four of the crowding scales were significantly correlated, but their predictive abilities varied widely. NEDOCS had the highest area under the receiver operating characteristic curve (AROC) (0.92), while EDCS had the lowest (0.64). The recommended thresholds for the crowding scales were rarely exceeded; therefore, the scales were adjusted to site-specific cut points. At a site-specific cut point of 37.19, NEDOCS had the highest sensitivity (0.81), specificity (0.87), and positive predictive value (0.62). Conclusions At the study site, the suggested thresholds of the published crowding scales did not agree with providers' perceptions of ED crowding. Even after adjusting the scales to site-specific thresholds, a relatively low prevalence of ED crowding resulted in unacceptably low positive predictive values for each scale. These results indicate that these crowding scales lack scalability and do not perform as designed in EDs where crowding is not the norm. However, two of the crowding scales, EDWIN and NEDOCS, and one of the READI subscales, bed ratio, yielded good predictive power (AROC >0.80) of perceived ED crowding, suggesting that they could be used effectively after a period of site-specific calibration at EDs where crowding is a frequent occurrence. [source]

    Gestational diabetes: fasting capillary glucose as a screening test in a multi-ethnic, high-risk population

    DIABETIC MEDICINE, Issue 8 2009
    M. M. Agarwal
    Abstract Aims, In populations at high risk of gestational diabetes mellitus (GDM), screening every pregnant woman by an oral glucose tolerance test (OGTT) is very demanding. The aim of this study was to determine the value of the fasting capillary glucose (FCG) as a screening test for GDM. Methods, FCG was measured by a plasma-correlated glucometer in 1465 pregnant women who underwent a one-step diagnostic 75-g OGTT for universal screening of GDM. Results, One hundred and ninety-six (13.4%) women had GDM as defined by the criteria of the American Diabetes Association. The area under the receiver operating characteristic curve (AUC) of the FCG was 0.83 (95% confidence interval 0.80,0.86). A FCG threshold of 4.7 mmol/l (at an acceptable sensitivity of 86.0%) independently could rule-out GDM in 731 (49.9%) women, while the FCG could rule-in GDM (100% specificity) in 16 (1.1%) additional women; therefore, approximately half of the women would not need to continue with the cumbersome OGTT. Conclusions, Screening using a FCG significantly reduces the number of OGTTs needed for the diagnosis of GDM. Wider assessment, particularly in low-risk populations, would confirm the potential value of the FCG as a screening test for GDM. [source]

    Long-term prognostic value of B-type natriuretic peptide in cardiac and non-cardiac causes of acute dyspnoea

    M. Christ
    Abstract Background, B-type natriuretic peptide (BNP) levels significantly predict increased risk of death in heart failure. The predictive role of BNP levels in patients with non-cardiac causes of acute dyspnoea presenting to the emergency department is not well characterized. Materials and methods, The B-type natriuretic peptide for Acute Shortness of Breath EvaLuation (BASEL) study enrolled consecutive patients with acute dyspnoea. Results, Cumulative mortality was 14·8%, 33·1% and 51·9% in 452 patients (age: 19,97 years; 58% male) within low (< 100 pg mL,1), intermediate (100,500 pg mL,1) and high (> 500 pg mL,1) BNP plasma levels at 18 months of follow-up. BNP classes (point estimate: 1·55, 95%CI: 1·19,2·03, P = 0·001) in addition to age, increased heart rate and diuretic use emerged as significant predictors for long-term mortality in multivariable Cox regression analyses. The BNP concentration alone had an area under the receiver operating characteristic curve of 0·71 (95%CI: 0·66,0·76; P < 0·001) for predicting 18 months mortality. BNP plasma levels independently predicted long-term risk of death in patients with non-cardiac (point estimate: 1·72, 95%CI: 1·16,2·56; P = 0·007) and with cardiac causes of acute dyspnoea (point estimate: 2·21, 95%CI: 1·34,3·64; P = 0·002). Conclusions, BNP levels are strong and independent predictors for long-term mortality in unselected dyspnoeic patients presenting to the emergency department independent from the cause of dyspnoea. [source]

    Brain natriuretic peptide in the prediction of recurrence of angina pectoris

    H. Takase
    Abstract Background, Circulating levels of brain natriuretic peptide (BNP) provide prognostic information for patients with heart failure, but little is known about its prognostic usefulness in patients with stable angina pectoris. We investigated whether BNP could be used as a marker for the prediction of anginal recurrence after successful treatment. Design, Brain natriuretic peptide levels of 77 patients with stable angina pectoris were measured at enrolment and after confirmation of successful treatment (i.e. no anginal attack for at least 6 months: chronic phase) with percutaneous transluminal coronary angioplasty and/or conventional medication. Then, we prospectively followed them up for 25·9 ± 1·4 months, with the endpoint being a recurrence of anginal attacks. Results, An anginal attack recurred in seven patients. In patients without recurrence, BNP levels in the chronic phase (21 ± 12 [median ± median absolute deviation] pg mL,1) were lower than those measured at enrolment (46 ± 25 pg mL,1, P < 0·0001), whereas the levels in patients with recurrence increased during the same period (from 36 ± 16 to 72 ± 42 pg mL,1, P < 0·05). A univariate analysis revealed that the BNP level measured in the chronic phase was the significant predictor of future anginal recurrence. Analysis of the receiver operating characteristic curve indicated that the cutoff level of BNP in the chronic phase was 68 pg mL,1. The Kaplan-Meier method revealed that the incidence of anginal recurrence was higher in patients with higher (71·4%) than lower levels of BNP (2·9%; P < 0·0001). Conclusions, Measurement of BNP levels after successful therapy is clinically useful for the prediction of recurrence of anginal attacks in patients with angina pectoris. [source]

    The contributions of topoclimate and land cover to species distributions and abundance: fine-resolution tests for a mountain butterfly fauna

    GLOBAL ECOLOGY, Issue 2 2010
    Javier Gutiérrez Illán
    ABSTRACT Aim, Models relating species distributions to climate or habitat are widely used to predict the effects of global change on biodiversity. Most such approaches assume that climate governs coarse-scale species ranges, whereas habitat limits fine-scale distributions. We tested the influence of topoclimate and land cover on butterfly distributions and abundance in a mountain range, where climate may vary as markedly at a fine scale as land cover. Location, Sierra de Guadarrama (Spain, southern Europe) Methods, We sampled the butterfly fauna of 180 locations (89 in 2004, 91 in 2005) in a 10,800 km2 region, and derived generalized linear models (GLMs) for species occurrence and abundance based on topoclimatic (elevation and insolation) or habitat (land cover, geology and hydrology) variables sampled at 100-m resolution using GIS. Models for each year were tested against independent data from the alternate year, using the area under the receiver operating characteristic curve (AUC) (distribution) or Spearman's rank correlation coefficient (rs) (abundance). Results, In independent model tests, 74% of occurrence models achieved AUCs of > 0.7, and 85% of abundance models were significantly related to observed abundance. Topoclimatic models outperformed models based purely on land cover in 72% of occurrence models and 66% of abundance models. Including both types of variables often explained most variation in model calibration, but did not significantly improve model cross-validation relative to topoclimatic models. Hierarchical partitioning analysis confirmed the overriding effect of topoclimatic factors on species distributions, with the exception of several species for which the importance of land cover was confirmed. Main conclusions, Topoclimatic factors may dominate fine-resolution species distributions in mountain ranges where climate conditions vary markedly over short distances and large areas of natural habitat remain. Climate change is likely to be a key driver of species distributions in such systems and could have important effects on biodiversity. However, continued habitat protection may be vital to facilitate range shifts in response to climate change. [source]

    Development and Validation of a Risk-Adjustment Tool in Acute Asthma

    Chu-Lin Tsai
    Objective. To develop and prospectively validate a risk-adjustment tool in acute asthma. Data Sources. Data were obtained from two large studies on acute asthma, the Multicenter Airway Research Collaboration (MARC) and the National Emergency Department Safety Study (NEDSS) cohorts. Both studies involved >60 emergency departments (EDs) and were performed during 1996,2001 and 2003,2006, respectively. Both included patients aged 18,54 years presenting to the ED with acute asthma. Study Design. Retrospective cohort studies. Data Collection. Clinical information was obtained from medical record review. The risk index was derived in the MARC cohort and then was prospectively validated in the NEDSS cohort. Principle Findings. There were 3,515 patients in the derivation cohort and 3,986 in the validation cohort. The risk index included nine variables (age, sex, current smoker, ever admitted for asthma, ever intubated for asthma, duration of symptoms, respiratory rate, peak expiratory flow, and number of beta-agonist treatments) and showed satisfactory discrimination (area under the receiver operating characteristic curve, 0.75) and calibration ( p=.30 for Hosmer,Lemeshow test) when applied to the validation cohort. Conclusions. We developed and validated a novel risk-adjustment tool in acute asthma. This tool can be used for health care provider profiling to identify outliers for quality improvement purposes. [source]

    Early on-treatment prediction of response to peginterferon alfa-2a for HBeAg-negative chronic hepatitis B using HBsAg and HBV DNA levels,

    HEPATOLOGY, Issue 2 2010
    Vincent Rijckborst
    Peginterferon alfa-2a results in a sustained response (SR) in a minority of patients with hepatitis B e antigen (HBeAg),negative chronic hepatitis B (CHB). This study investigated the role of early on-treatment serum hepatitis B surface antigen (HBsAg) levels in the prediction of SR in HBeAg-negative patients receiving peginterferon alfa-2a. HBsAg (Architect from Abbott) was quantified at the baseline and during treatment (weeks 4, 8, 12, 24, 36, and 48) and follow-up (weeks 60 and 72) in the sera from 107 patients who participated in an international multicenter trial (peginterferon alfa-2a, n = 53, versus peginterferon alfa-2a and ribavirin, n = 54). Overall, 24 patients (22%) achieved SR [serum hepatitis B virus (HBV) DNA level < 10,000 copies/mL and normal alanine aminotransferase levels at week 72]. Baseline characteristics were comparable between sustained responders and nonresponders. From week 8 onward, serum HBsAg levels markedly decreased in sustained responders, whereas only a modest decline was observed in nonresponders. However, HBsAg declines alone were of limited value in the prediction of SR [area under the receiver operating characteristic curve (AUC) at weeks 4, 8, and 12 = 0.59, 0.56, and 0.69, respectively]. Combining the declines in HBsAg and HBV DNA allowed the best prediction of SR (AUC at week 12 = 0.74). None of the 20 patients (20% of the study population) in whom a decrease in serum HBsAg levels was absent and whose HBV DNA levels declined less than 2 log copies/mL exhibited an SR (negative predictive value = 100%). Conclusion: At week 12 of peginterferon alfa-2a treatment for HBeAg-negative CHB, a solid stopping rule was established with a combination of declines in serum HBV DNA and HBsAg levels from the baseline. Quantitative serum HBsAg in combination with HBV DNA enables on-treatment adjustments of peginterferon therapy for HBeAg-negative CHB. (HEPATOLOGY 2010) [source]

    Liver stiffness identifies two different patterns of fibrosis progression in patients with hepatitis C virus recurrence after liver transplantation,

    HEPATOLOGY, Issue 1 2010
    José A. Carrión
    Significant liver fibrosis (F , 2) and portal hypertension (hepatic venous pressure gradient [HVPG] , 6 mmHg) at 1 year after liver transplantation (LT) identify patients with severe hepatitis C recurrence. We evaluated whether repeated liver stiffness measurements (LSM) following LT can discriminate between slow and rapid "fibrosers" (fibrosis stage F2-F4 at 1 year after LT). Eighty-four patients who had undergone LT and who were infected with hepatitis C virus (HCV) and 19 LT controls who were not infected with HCV underwent LSM at 3, 6, 9, and 12 months after LT. All HCV-infected patients underwent liver biopsy 12 months after LT (paired HVPG measurements in 74); 31 (37%) were rapid fibrosers. Median LSM (in kilopascal) at months 6, 9, and 12 were significantly higher in rapid fibrosers (9.9, 9.5, 12.1) than in slow fibrosers (6.9, 7.5, 6.6) (P < 0.01 all time points). The slope of liver stiffness progression (kPa × month) in rapid fibrosers (0.42) was significantly greater than in slow fibrosers (0.05) (P < 0.001), suggesting two different speeds of liver fibrosis progression. Figures were almost identical for patients with HVPG , 6 mmHg or HVPG < 6 mmHg at 1 year after LT. Multivariate analysis identified donor age, bilirubin level, and LSM as independent predictors of fibrosis progression and portal hypertension in the estimation group (n = 50) and were validated in a second group of 34 patients. The areas under the receiver operating characteristic curve that could identify rapid fibrosers and patients with portal hypertension as early as 6 months after LT were 0.83 and 0.87, respectively, in the estimation group and 0.75 and 0.80, respectively, in the validation group. Conclusion: Early and repeated LSM following hepatitis C recurrence in combination with clinical variables discriminates between rapid and slow fibrosers after LT. (HEPATOLOGY 2009.) [source]

    Predictors of response to therapy with terlipressin and albumin in patients with cirrhosis and type 1 hepatorenal syndrome,

    HEPATOLOGY, Issue 1 2010
    André Nazar
    Terlipressin plus albumin is an effective treatment for type 1 hepatorenal syndrome (HRS), but approximately only half of the patients respond to this therapy. The aim of this study was to assess predictive factors of response to treatment with terlipressin and albumin in patients with type 1 HRS. Thirty-nine patients with cirrhosis and type 1 HRS were treated prospectively with terlipressin and albumin. Demographic, clinical, and laboratory variables obtained before the initiation of treatment as well as changes in arterial pressure during treatment were analyzed for their predictive value. Response to therapy (reduction in serum creatinine <1.5 mg/dL at the end of treatment) was observed in 18 patients (46%) and was associated with an improvement in circulatory function. Independent predictive factors of response to therapy were baseline serum bilirubin and an increase in mean arterial pressure of ,5 mm Hg at day 3 of treatment. The cutoff level of serum bilirubin that best predicted response to treatment was 10 mg/dL (area under the receiver operating characteristic curve, 0.77; P < 0.0001; sensitivity, 89%; specificity, 61%). Response rates in patients with serum bilirubin <10 mg/dL or ,10 mg/dL were 67% and 13%, respectively (P = 0.001). Corresponding values in patients with an increase in mean arterial pressure ,5 mm Hg or <5 mm Hg at day 3 were 73% and 36%, respectively (P = 0.037). Conclusion: Serum bilirubin and an early increase in arterial pressure predict response to treatment with terlipressin and albumin in type 1 HRS. Alternative treatment strategies to terlipressin and albumin should be investigated for patients with type 1 HRS and low likelihood of response to vasoconstrictor therapy. (HEPATOLOGY 2009.) [source]

    SAFE biopsy: A validated method for large-scale staging of liver fibrosis in chronic hepatitis C,

    HEPATOLOGY, Issue 6 2009
    Giada Sebastiani
    The staging of liver fibrosis is pivotal for defining the prognosis and indications for therapy in hepatitis C. Although liver biopsy remains the gold standard, several noninvasive methods are under evaluation for clinical use. The aim of this study was to validate the recently described sequential algorithm for fibrosis evaluation (SAFE) biopsy, which detects significant fibrosis (,F2 by METAVIR) and cirrhosis (F4) by combining the AST-to-platelet ratio index and Fibrotest-Fibrosure, thereby limiting liver biopsy to cases not adequately classifiable by noninvasive markers. Hepatitis C virus (HCV) patients (2035) were enrolled in nine locations in Europe and the United States. The diagnostic accuracy of SAFE biopsy versus histology, which is the gold standard, was investigated. The reduction in the need for liver biopsies achieved with SAFE biopsy was also assessed. SAFE biopsy identified significant fibrosis with 90.1% accuracy (area under the receiver operating characteristic curve = 0.89; 95% confidence interval, 0.87-0.90) and reduced by 46.5% the number of liver biopsies needed. SAFE biopsy had 92.5% accuracy (area under the receiver operating characteristic curve = 0.92; 95% confidence interval, 0.89-0.94) for the detection of cirrhosis, obviating 81.5% of liver biopsies. A third algorithm identified significant fibrosis and cirrhosis simultaneously with high accuracy and a 36% reduction in the need for liver biopsy. The patient's age and body mass index influenced the performance of SAFE biopsy, which was improved with adjusted Fibrotest-Fibrosure cutoffs. Two hundred two cases (9.9%) had discordant results for significant fibrosis with SAFE biopsy versus histology, whereas 153 cases (7.5%) were discordant for cirrhosis detection; 71 of the former cases and 56 of the latter cases had a Fibroscan measurement within 2 months of histological evaluation. Fibroscan confirmed SAFE biopsy findings in 83.1% and 75%, respectively. Conclusion: SAFE biopsy is a rational and validated method for staging liver fibrosis in hepatitis C with a marked reduction in the need for liver biopsy. It is an attractive tool for large-scale screening of HCV carriers. (HEPATOLOGY 2009.) [source]

    B-type natriuretic peptide as an indicator of right ventricular dysfunction in acute pulmonary embolism,

    T. Yardan
    Summary Objective:, B-type natriuretic peptide (BNP) is a neurohormone secreted from cardiac ventricles in response to ventricular strain. The aim of present study was to evaluate the role of BNP in the diagnosis of the right ventricular (RV) dysfunction in acute pulmonary embolism (PE). Methods:, BNP levels were measured in patients with acute PE as diagnosed by high probability lung scan or positive spiral computed tomography. All patients underwent standard echocardiography and blood tests during the second hour of the diagnosis. Results:, Forty patients diagnosed as acute PE (mean age, 60.4 ± 13.2 years; 62.5% women) were enrolled in this study. Patients with RV dysfunction had significantly higher BNP levels than patients without RV dysfunction (426 ± 299.42 pg/ml vs. 39.09 ± 25.22 pg/ml, p < 0.001). BNP-discriminated patients with or without RV dysfunction (area under the receiver operating characteristic curve, 0.943; 95% CI, 0.863,1.022). BNP > 90 pg/ml was associated with a risk ratio of 165 (95% CI, 13.7,1987.2) for the diagnosis of RV dysfunction. There was a significant correlation between RV end-diastolic diameter and BNP (r = 0.89, p < 0.001). Sixteen patients (40%) were diagnosed as having low-risk PE, 19 patients (47.5%) with submassive PE and five patients (12.5%) with massive PE. The mean BNP was 39.09 ± 25.2, 378.4 ± 288.4 and 609.2 ± 279.2 pg/ml in each group respectively. Conclusion:, Measurement of BNP levels may be a useful approach in diagnosis of RV dysfunction in patients with acute PE. The possibility of RV dysfunction in patients with plasma BNP levels > 90 pg/ml should be strongly considered. [source]

    Prospective cohort study comparing sequential organ failure assessment and acute physiology, age, chronic health evaluation III scoring systems for hospital mortality prediction in critically ill cirrhotic patients

    Y-C Chen
    Summary The aim of the study was to evaluate the usefulness of sequential organ failure assessment (SOFA) and acute physiology, age, chronic health evaluation III (APACHE III) scoring systems obtained on the first day of intensive care unit (ICU) admission in predicting hospital mortality in critically ill cirrhotic patients. The study enrolled 102 cirrhotic patients consecutively admitted to ICU during a 1-year period. Twenty-five demographic, clinical and laboratory variables were analysed as predicators of survival. Information considered necessary to calculate the Child,Pugh, SOFA and APACHE III scores on the first day of ICU admission was also gathered. Overall hospital mortality was 68.6%. Multiple logistic regression analysis revealed that mean arterial pressure, SOFA and APACHE III scores were significantly related to prognosis. Goodness-of-fit was good for the SOFA and APACHE III models. Both predictive models displayed a similar degree of the best Youden index (0.68) and overall correctness (84%) of prediction. The SOFA and APACHE III models displayed good areas under the receiver,operating characteristic curve (0.917 ± 0.028 and 0.912 ± 0.029, respectively). Finally, a strong and significant positive correlation exists between SOFA and APACHE III scores for individual patients (r2 = 0.628, p < 0.001). This investigation confirms the grave prognosis for cirrhotic patients admitted to ICU. Both SOFA and APACHE III scores are excellent tools to predict the hospital mortality in critically ill cirrhotic patients. The overall predictive accuracy of SOFA and APACHE III is superior to that of Child,Pugh system. The role of these scoring systems in describing the dynamic aspects of clinical courses and allocating ICU resources needs to be clarified. [source]

    Screening for serious mental illness in the general population with the K6 screening scale: results from the WHO World Mental Health (WMH) survey initiative

    Ronald C. Kessler
    Abstract Data are reported on the background and performance of the K6 screening scale for serious mental illness (SMI) in the World Health Organization (WHO) World Mental Health (WMH) surveys. The K6 is a six-item scale developed to provide a brief valid screen for Diagnostic and Statistical Manual of Mental Disorders 4th edition (DSM-IV) SMI based on the criteria in the US ADAMHA Reorganization Act. Although methodological studies have documented good K6 validity in a number of countries, optimal scoring rules have never been proposed. Such rules are presented here based on analysis of K6 data in nationally or regionally representative WMH surveys in 14 countries (combined N = 41,770 respondents). Twelve-month prevalence of DSM-IV SMI was assessed with the fully-structured WHO Composite International Diagnostic Interview. Nested logistic regression analysis was used to generate estimates of the predicted probability of SMI for each respondent from K6 scores, taking into consideration the possibility of variable concordance as a function of respondent age, gender, education, and country. Concordance, assessed by calculating the area under the receiver operating characteristic curve, was generally substantial (median 0.83; range 0.76,0.89; inter-quartile range 0.81,0.85). Based on this result, optimal scaling rules are presented for use by investigators working with the K6 scale in the countries studied. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Validity of the World Health Organization Adult ADHD Self-Report Scale (ASRS) Screener in a representative sample of health plan members

    Ronald C. Kessler
    Abstract The validity of the six-question World Health Organization Adult ADHD Self-Report Scale (ASRS) Screener was assessed in a sample of subscribers to a large health plan in the US. A convenience subsample of 668 subscribers was administered the ASRS Screener twice to assess test-retest reliability and then a third time in conjunction with a clinical interviewer for DSM-IV adult ADHD. The data were weighted to adjust for discrepancies between the sample and the population on socio-demographics and past medical claims. Internal consistency reliability of the continuous ASRS Screener was in the range 0.63,0.72 and test-retest reliability (Pearson correlations) in the range 0.58,0.77. A four-category version The ASRS Screener had strong concordance with clinician diagnoses, with an area under the receiver operating characteristic curve (AUC) of 0.90. The brevity and ability to discriminate DSM-IV cases from non-cases make the six-question ASRS Screener attractive for use both in community epidemiological surveys and in clinical outreach and case-finding initiatives. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Accuracy of Spirometry in Diagnosing Pulmonary Restriction in Elderly People

    Simone Scarlata MD
    OBJECTIVES: To compare the accuracy of a diagnosis of pulmonary restriction made using forced vital capacity (FVC) less than the lower limit of normal (LLN) with the criterion standard diagnosis made using total lung capacity (TLC) less than the LLN in an elderly population. DESIGN: Retrospective analysis. SETTING: A teaching hospital. PARTICIPANTS: Five hundred sixty-four ambulatory and acute care hospital patients aged 65 to 96 underwent complete pulmonary function evaluation. MEASUREMENTS: Sensitivity, specificity, positive and negative predictive values (PPV, NPV) of diagnosis of pulmonary restriction defined as FVC less than the LLN were calculated in the overall sample and after stratification according to bronchial obstruction. Expected PPV and NPV at different background prevalence of true pulmonary restriction (5% and 15%) were calculated using the Bayes theorem. RESULTS: Low sensitivity (0.32) and high specificity (0.95) were found, with an area under the receiver operating characteristic curve (AUC) of 0.89. In participants without bronchial obstruction, specificity was even higher, although sensitivity decreased to 0.28 (AUC=0.92). The PPV was good (0.81), whereas with a low to moderate a priori probability (prevalence from 5% to 15%) the NPV was fair (,0.89). CONCLUSION: A reduction in FVC below LLN cannot reliably identify true pulmonary restriction in elderly people, confirming previous findings in the adult population. Normal FVC, instead, can effectively exclude pulmonary restriction regardless of the presence of bronchial obstruction when the a priori probability is low or moderately high. [source]

    Detection of Mild Hyposalivation in Elderly People Based on the Chewing Time of Specifically Designed Disc Tests: Diagnostic Accuracy

    DrOdont, Isabelle Madinier DDS
    OBJECTIVES: To compare sialometry with chewing time (including swallowing) of specifically designed disc tests. DESIGN: Index test versus reference standard (sialometry; 60 patients); reliability study (10 patients). SETTING: Outpatient dental clinic and geriatric ward, Nice University Hospital, France. PARTICIPANTS: Thirty adults and 30 older patients (mean ages 47 and 84). INTERVENTION: Index test assessment in patients with and without hyposalivation. MEASUREMENTS: Data from medical files, interviews and oral examination were collected. Sialometry (stimulated salivary flow rate (SSFR) mL/min) and disc chewing times (seconds) were measured. RESULTS: Sialometry was too long and was inappropriate for five of the 30 older persons. Chewing times were negatively correlated to sialometry results (Spearman correlation coefficient (R)=0.77, P<.001). The threshold to diagnose hyposalivation (SSFR <1 mL/min) was 40 seconds (area under the receiver operating characteristic curve (AUC)=0.921, 100% sensitivity, 72% specificity). Twenty-seven subjects with a SSFR less than 1.5 mL/min had a chewing time longer than 40 seconds, suggesting that mild hyposalivation and eating difficulties were related (AUC=0.941, 93% sensitivity, 88% specificity). Mean chewing time was greater with xerostomia (51.9 vs 30.7 seconds, P<.001) but not with dental pain (39.5 vs 39.9, P=.96). Masticatory percentage (e.g., pairs of antagonistic teeth) had no effect on chewing time (SSFR <1 mL/min, AUC=0.921; SSFR <1.5 mL/min, AUC=0.950). Reliability was better for the disc test than for sialometry (intraclass correlation 0.85 vs 0.70). CONCLUSION: This disc test was conceived to detect mild hyposalivation in geriatric patients with impaired dental health. Early detection of hyposalivation could help to suppress or avoid xerostomia-inducing drugs and to prevent oral infections and dental caries. [source]

    The Identification of Seniors At Risk Screening Tool: Further Evidence of Concurrent and Predictive Validity

    Nandini Dendukuri PhD
    Objectives: To evaluate the validity of the Identification of Seniors at Risk (ISAR) screening tool for detecting severe functional impairment and depression and predicting increased depressive symptoms and increased utilization of health services. Setting: Four university-affiliated hospitals in Montreal. Design: Data from two previous studies were available: Study 1, in which the ISAR scale was developed (n=1,122), and Study 2, in which it was used to identify patients for a randomized trial of a nursing intervention (n=1,889 with administrative data, of which 520 also had clinical data). Participants: Patients aged 65 and older who were to be released from an emergency department (ED). Measurements: Baseline validation criteria included premorbid functional status in both studies and depression in Study 2 only. Increase in depressive symptoms at 4-month follow-up was assessed in Study 2. Information on health services utilization during the 5 months after the ED visit (repeat ED visits and hospitalization in both studies, visits to community health centers in Study 2) was available by linkage with administrative databases. Results: Estimates of the area under the receiver operating characteristic curve (AUC) for concurrent validity of the ISAR scale for severe functional impairment and depression ranged from 0.65 to 0.86. Estimates of the AUC for predictive validity for increased depressive symptoms and high utilization of health services ranged from 0.61 to 0.71. Conclusion: The ISAR scale has acceptable to excellent concurrent and predictive validity for a variety of outcomes, including clinical measures and utilization of health services. [source]

    Model-based uncertainty in species range prediction

    Richard G. Pearson
    Abstract Aim, Many attempts to predict the potential range of species rely on environmental niche (or ,bioclimate envelope') modelling, yet the effects of using different niche-based methodologies require further investigation. Here we investigate the impact that the choice of model can have on predictions, identify key reasons why model output may differ and discuss the implications that model uncertainty has for policy-guiding applications. Location, The Western Cape of South Africa. Methods, We applied nine of the most widely used modelling techniques to model potential distributions under current and predicted future climate for four species (including two subspecies) of Proteaceae. Each model was built using an identical set of five input variables and distribution data for 3996 sampled sites. We compare model predictions by testing agreement between observed and simulated distributions for the present day (using the area under the receiver operating characteristic curve (AUC) and kappa statistics) and by assessing consistency in predictions of range size changes under future climate (using cluster analysis). Results, Our analyses show significant differences between predictions from different models, with predicted changes in range size by 2030 differing in both magnitude and direction (e.g. from 92% loss to 322% gain). We explain differences with reference to two characteristics of the modelling techniques: data input requirements (presence/absence vs. presence-only approaches) and assumptions made by each algorithm when extrapolating beyond the range of data used to build the model. The effects of these factors should be carefully considered when using this modelling approach to predict species ranges. Main conclusions, We highlight an important source of uncertainty in assessments of the impacts of climate change on biodiversity and emphasize that model predictions should be interpreted in policy-guiding applications along with a full appreciation of uncertainty. [source]

    Vascular Function Measured by Fingertip Thermal Reactivity Is Impaired in Patients With Metabolic Syndrome and Diabetes Mellitus

    Naser Ahmadi MD
    Digital thermal monitoring (DTM) of vascular function has already been shown to correlate well with coronary artery calcium (CAC) score and coronary artery disease. To determine its utility in the metabolic syndrome (MS) and diabetes mellitus (DM), 233 asymptomatic patients with DM/MS but without coronary artery disease underwent DTM during and after 5 minutes of supra-systolic arm cuff inflation, as well as CAC. Post-cuff deflation adjusted temperature rebound (aTR) was lower in MS and DM compared with the normal group. The odds ratio of lowest vs upper 2 tertiles of aTR was 2.3 for MS and 3.5 for DM compared with the normal group, independent of age, sex, and risk factors. The area under the receiver operating characteristic curve to predict CAC ,100 was 0.69 for metabolic status (DM/MS), 0.79 for aTR, and 0.87 for both. This study demonstrates that vascular dysfunction measured by DTM is associated with DM/MS and could potentially be used to detect asymptomatic individuals with increased subclinical atherosclerosis. [source]

    Development of a simple scoring tool in the primary care setting for prediction of recurrent falls in men and women aged 65 years and over living in the community

    Jean Woo
    Aim., We documented the number of falls and falls risk profile over two years to derive a falls risks prediction score. Background., Simple falls risk assessment tools not requiring equipment or trained personnel may be used as a first step in the primary care setting to identify older people at risk who may be referred for further falls risk assessment in special clinics. Design., Survey. Method., Men (n = 1941) and 1949 women aged 65 years and over living in the community were followed up for two years to document the number of falls. Information was collected regarding demography, socioeconomic status, medical history, functional limitations, lifestyle factors and psychosocial functioning. Measurements include body mass index, grip strength and stride length. Logistic regression was used to determine significant predictions of falls and to calculate predictive scores. Result., Twelve factors in men and nine factors in women were used to construct a risk score. The AUC of the receiver operating characteristic curve was >0·70 for both men and women and a cut off score of ,8 gave sensitivity and specificity values between 60,78%. The factors included chronic disease, drugs, functional limitation, lifestyle, education and psychosocial factors. When applied to future predictions, only low energy level and clumsiness in both hands in men and feeling downhearted in women, were significant factors. Conclusions., A risk assessment tool with a cut off score of ,8 developed from a two-year prospective study of falls may be used in the community setting as an initial first step for screening out those at low risk of falls. Relevance to clinical practice., A simple tool may be used in the community to screen out those at risk for falls, concentrating trained healthcare professionals' time on detailed falls assessment and intervention for those classified as being at risk. [source]

    Novel parameter for the diagnosis of distal middle cerebral artery stenosis with transcranial Doppler sonography

    Suk-Won Ahn MD
    Abstract Purpose Transcranial Doppler sonography (TCD) is commonly used for the diagnosis of middle cerebral artery (MCA) stenosis. However, TCD indices to predict distal MCA (M2) stenosis have not yet been established. We compared TCD and magnetic resonance angiography (MRA) to validate a new index for the diagnosis of M2 stenosis. Methods Consecutive patients who underwent TCD and MRA were included. Based on MRA, M2 stenosis was defined as >50% narrowing beyond the bifurcation area. TCD index of the M2/M1 ratio was defined as the ratio between the mean flow velocity (MFV) obtained at a depth of 30,44 mm (M2) and a depth of 45,65 mm (M1). Sensitivity and specificity of the M2/M1 ratio were calculated from the receiver operating characteristic curve. The diagnostic yield of elevated MFV (>80 cm/s) and asymmetry index of >30% for M2 stenosis were also investigated. Results Among the consecutive patients, 105 with M2 stenosis were compared with 123 without MCA stenosis. The M2/M1 ratio was significantly higher in the M2 stenosis group (1.10 versus 0.86, p < 0.001). Sensitivity and specificity for M2 stenosis were most satisfying when the M2/M1 ratio of 0.97 was adopted as the cutoff value. Diagnostic yield of the M2/M1 ratio was better than MFV or asymmetry index. Conclusions The M2/M1 ratio may be a highly specific parameter for assessing M2 stenosis with TCD. © 2010 Wiley Periodicals, Inc. J Clin Ultrasound 38:420,425, 2010 [source]

    Pharmacokinetic mapping for lesion classification in dynamic breast MRI

    Matthias C. Schabel PhD
    Abstract Purpose: To prospectively investigate whether a rapid dynamic MRI protocol, in conjunction with pharmacokinetic modeling, could provide diagnostically useful information for discriminating biopsy-proven benign lesions from malignancies. Materials and Methods: Patients referred to breast biopsy based on suspicious screening findings were eligible. After anatomic imaging, patients were scanned using a dynamic protocol with complete bilateral breast coverage. Maps of pharmacokinetic parameters representing transfer constant (Ktrans), efflux rate constant (kep), blood plasma volume fraction (vp), and extracellular extravascular volume fraction (ve) were averaged over lesions and used, with biopsy results, to generate receiver operating characteristic curves for linear classifiers using one, two, or three parameters. Results: Biopsy and imaging results were obtained from 93 lesions in 74 of 78 study patients. Classification based on Ktrans and kep gave the greatest accuracy, with an area under the receiver operating characteristic curve of 0.915, sensitivity of 91%, and specificity of 85%, compared with values of 88% and 68%, respectively, obtained in a recent study of clinical breast MRI in a similar patient population. Conclusion: Pharmacokinetic classification of breast lesions is practical on modern MRI hardware and provides significant accuracy for identification of malignancies. Sensitivity of a two-parameter linear classifier is comparable to that reported in a recent multicenter study of clinical breast MRI, while specificity is significantly higher. J. Magn. Reson. Imaging 2010;31:1371,1378. © 2010 Wiley-Liss, Inc. [source]

    Accuracy of MRI for predicting the circumferential resection margin, mesorectal fascia invasion, and tumor response to neoadjuvant chemoradiotherapy for locally advanced rectal cancer

    Seung Ho Kim MD
    Abstract Purpose To evaluate the diagnostic accuracy of MRI for predicting the circumferential resection margin (CRM), mesorectal fascia (MRF) invasion, and the tumor response to neoadjuvant chemoradiotherapy (CRT) for locally advanced rectal cancer. Materials and Methods Sixty-five consecutive patients with locally advanced rectal cancer (,T3 or lymph node-positive) who underwent neoadjuvant CRT and subsequent surgery were enrolled in this retrospective study. Two blinded radiologists independently reviewed both the pre- and post-CRT rectal MR images and measured the post-CRT CRM; they recorded their confidence level with respect to the MRF invasion and tumor response using a 5-point scale. The diagnostic accuracy of each reviewer was calculated using receiver operating characteristic curve (ROC) analysis. Results The measured CRM was not significantly different from the reference standard (mean difference, ,1.4 mm; 95% limits of agreement, ,8.3,5.4 mm; interclass correlation coefficient, 0.82). The diagnostic accuracy (Az) for determining MRF invasion was 0.890 for reviewer 1 (95% confidence interval [CI], 0.788,0.954) and 0.829 for reviewer 2 (95% CI, 0.715,0.911). The Az for predicting complete or near-complete regression was 0.791 for reviewer 1 (95% CI, 0.672,0.882) and 0.735 for reviewer 2 (95% CI, 0.611,0.837). Conclusion MRI provides accurate information regarding the CRM of locally advanced rectal cancer after neoadjuvant CRT; it also shows relatively high accuracy for predicting MRF invasion and moderate accuracy for assessing tumor response. J. Magn. Reson. Imaging 2009;29:1093,1101. © 2009 Wiley-Liss, Inc. [source]

    Platelet concentrates transfusion in cardiac surgery and platelet function assessment by multiple electrode aggregometry

    Background: Platelet dysfunction contributes to the pathophysiology of bleeding complications during and after cardiac surgery. In most surgical institutions, no peri-operative point-of-care monitoring of platelet function is used. We evaluated the usefulness of the Multiplate® platelet function analyser based on impedance aggregometry for identifying groups of patients at a high risk of transfusion of platelet concentrates (PC). Methods: Platelet function parameters were determined in 60 patients before and after routine cardiac surgery. Impedance aggregometry measurements were performed on Multiplate® using ADP (ADPtest), collagen (COLtest) and thrombin receptor activating peptide (TRAPtest) as platelet activators. The correlations between the aggregometry results and the transfusion of PC were calculated. The results of the aggregation tests were also divided into tertiles and the differences in PC transfusion between the low and the high tertile were assessed. Results: Low aggregometry delimited groups of patients with significantly higher PC transfusion. In the receiver operating characteristic curve, low pre-operative aggregation in the ADPtest identified patients with high total transfusion of PC (area under the curve 0.74, P=0.001), while the ADPtest performed at the end of the operation identified patients with high PC transfusion on the intensive care unit (ICU) (area under the curve 0.76, P=0.002). Conclusions: Near-patient platelet aggregation may allow the identification of patients with enhanced risk of PC transfusion, both pre-operatively and upon arrival on the ICU. [source]

    Comparative study of four candidate strategies to detect cervical cancer in different health care settings

    Meherbano M. Kamal
    Abstract Aim:, Considering the differing but potentially supplementary properties of visual inspection of the cervix with acetic acid (VIA) and the cytological examination (CYTO) of cervical smears for the screening of cervical cancers, we examined the performance of these two tests and their combinations for the screening of cervical cancer in different health care settings. Methods:, In this cross-sectional diagnostic test performance evaluation study of 4235 female subjects in the reproductive age group, we assessed the screening performance of four strategies: VIA alone, CYTO alone, VIA and CYTO combined in a parallel fashion, and VIA and CYTO combined in tandem. Subjects were recruited from three settings: Hospital, Urban Community and Rural Community. Colposcopy was used as the reference standard. Screening performance was assessed using sensitivity, specificity, post-test probabilities and likelihood ratios (LR), diagnostic odds, area under receiver operating characteristic curve and LR ,2. Results:, Both VIA and CYTO when used alone had a low sensitivity but high specificity, especially in the Rural Community setting. A combination of the results of VIA and CYTO improved the diagnostic accuracy but the strategy using a parallel combination of VIA and CYTO was the most accurate. In general, all screening strategies using VIA and CYTO showed a modest screening performance. Conclusions:, In the settings of varying levels of health care and low resources, caution is needed for a generalized use of VIA for cervical cancer screening. Further evaluation of the cost-effective ways of combining VIA and CYTO is needed in these circumstances. [source]

    Assessing accuracy of a continuous screening test in the presence of verification bias

    Todd A. Alonzo
    Summary., In studies to assess the accuracy of a screening test, often definitive disease assessment is too invasive or expensive to be ascertained on all the study subjects. Although it may be more ethical or cost effective to ascertain the true disease status with a higher rate in study subjects where the screening test or additional information is suggestive of disease, estimates of accuracy can be biased in a study with such a design. This bias is known as verification bias. Verification bias correction methods that accommodate screening tests with binary or ordinal responses have been developed; however, no verification bias correction methods exist for tests with continuous results. We propose and compare imputation and reweighting bias-corrected estimators of true and false positive rates, receiver operating characteristic curves and area under the receiver operating characteristic curve for continuous tests. Distribution theory and simulation studies are used to compare the proposed estimators with respect to bias, relative efficiency and robustness to model misspecification. The bias correction estimators proposed are applied to data from a study of screening tests for neonatal hearing loss. [source]