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Mean Bias (mean + bias)
Terms modified by Mean Bias Selected AbstractsPulsed dye densitometry with two different sensor types for cardiac output measurement after cardiac surgery: a comparison with the thermodilution techniqueACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2004C. K. Hofer Background:, Assessment of cardiac output (CO) by the indocyanine green (ICG) dye dilution technique (IDD) with transcutaneous signal detection may be a less invasive alternative to the pulmonary artery catheter (PAC). The aim of this study was to determine the accuracy and reliability of the DDG2001 analyzer (Nihon Kohden Corp, Tokyo, Japan) using a finger (IDDf) and a nose (IDDn) sensor as compared with the thermodilution technique by PAC. Methods:, In 31 consecutive patients after routine cardiac surgery, CO measurements were performed by IDD compared with the thermodilution technique following postoperative haemodynamic stabilization in the intensive care unit. Repeated measurements were made at 30-min intervals. CO was determined by iced water bolus (IWB: mean of three repeated injections) and IDDf or IDDn, respectively (mean of three repeated ICG injections). Results:, Thirty-three per cent of all measurements for IDDf and 9% for IDDn failed due to a missing signal detection. Mean bias for IDDf to IWB was ,0.5 l min,1·m,2 (limits of agreement: ,1.8/0.8 l min,1·m,2) and for IDDn to IWB was ,0.1 l min,1·m,2 (limits of agreement: ,1.6/1.5 l min,1·m,2). Correlation between IDDf and IWB (r = 0.2) was found to be inferior to the correlation between IDDn and IWB (r = 0.5). Conclusion:, The IDD showed a systematic bias compared with the IWB and its performance was limited due to signal detection failure. Therefore, the DDG2001 analyzer cannot be recommended as a substitute for the PAC in routine monitoring of cardiac output after cardiac surgery. [source] Body composition in older orthopaedic rehabilitation inpatients: Are field methods valid?NUTRITION & DIETETICS, Issue 3 2010Alison YAXLEY Abstract Aim:, The assessment of body composition is an important aspect of the determination of nutritional health. This cross-sectional measurement study aimed to assess the relative validity of a range of field techniques for the measurement of body composition in a sample of older orthopaedic inpatients participating in rehabilitation. Methods:, Assessment of percent fat-free mass of 31 adults, aged 65 years and over, was conducted under fasting conditions by two types of bioelectrical impedance analysis (multi-frequency and single frequency,using manufacturer's pre-programmed prediction equation) and compared with percent fat-free mass estimated by dual energy X-ray absorptiometry, a reference technique. Data from multi-frequency bioelectrical impedance analysis were also used to calculate percent fat-free mass from the prediction equation of Dey et al. for comparison. Skeletal muscle mass was derived from assessment of corrected arm muscle area and compared with skeletal muscle mass from dual energy X-ray absorptiometry analysis. Bland-Altman analysis was performed to determine the level of agreement between each field technique and dual energy X-ray absorptiometry. Results:, Mean bias and limits of agreement between single frequency bioelectrical impedance analysis and dual energy X-ray absorptiometry were ,5.7% (,24.0, 12.6), between multi-frequency bioelectrical impedance analysis (manufacturer's pre-programmed prediction equation) and dual energy X-ray absorptiometry were 1.4% (,13.4, 16.1), between multi-frequency bioelectrical impedance analysis (Dey et al. prediction equation) and dual energy X-ray absorptiometry were ,5.0% (,16.6, 6.6) and between skeletal muscle mass as derived from assessment of corrected arm muscle area and skeletal muscle mass from dual energy X-ray absorptiometry analysis ,0.97 kg (,8.37, 6.43). Conclusion:, None of the methods assessed are clinically acceptable for assessment of body composition in older orthopaedic rehabilitation patients; however, estimation of skeletal muscle mass, as derived from corrected arm muscle area, is likely to be of more use in the clinical setting as there is no requirement for patients to be fasted. [source] Evaluation of a single-platform microcapillary flow cytometer for enumeration of absolute CD4+ T-lymphocyte counts in HIV-1 infected Thai patients,,CYTOMETRY, Issue 5 2007Kovit Pattanapanyasat Abstract Background: Various assays are used to enumerate peripheral blood absolute CD4+ T-lymphocytes. Flow cytometry is considered the gold standard for this purpose. However, the high cost of available flow cytometers and monoclonal antibody reagents make it difficult to implement such methods in the resource-poor settings. In this study, we evaluated a cheaper, recently developed single-platform microcapillary cytometer for CD4+ T-lymphocyte enumeration, the personal cell analyzer (PCA), from Guava® Technologies. Methods: CD4+ and CD8+ T-lymphocyte counts in whole blood samples from 250 HIV-1 infected Thais were determined, using a two-color reagent kit and the Guava PCA, and compared with the results obtained with two reference microbead-based methods from Becton Dickinson Biosciences: the three-color TruCOUNTÔ tube method and the two-color FACSCountÔ method. Statistical correlations and agreements were determined using linear correlation and Bland,Altman analysis. Results: Absolute CD4+ T-lymphocyte counts obtained using the Guava PCA method highly correlated with those obtained using TruCOUNT method (R2 = 0.95, mean bias +13.1 cells/,l, limit of agreement [LOA] ,101.8 to +168.3 cells/,l). Absolute CD8+ T-lymphocyte counts obtained using the Guava PCA method also highly correlated with those obtained with the two reference methods (R2 = 0.92 and 0.88, respectively). Conclusion: This study shows that the enumeration of CD4+ T-lymphocytes using the Guava microcapillary cytometer PCA method performed well when compared with the two reference bead-based methods. However, like the two reference methods, this new method needs substantial technical expertise. © 2007 Clinical Cytometry Society. [source] Empirical models of UV total radiation and cloud effect studyINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2010David Mateos Villán Abstract Several empirical models of hourly ultraviolet total radiation (UVT) have been proposed in this study. Measurements of UVT radiation, 290,385 nm, have been recorded at ground level from February 2001 to June 2008 in Valladolid, Spain (latitude 41°40,N, longitude 4°50,W and 840 m a.s.l.). The empirical models have emerged due to the lack of some radiometric variables in measuring stations. Hence, good forecasts of them can be obtained from usual measures in these stations. Therefore, some advantages of the empirical models are that they allow the estimation of past missing data in the database and the forecast of future ultraviolet solar availability. In this study, reported models in the bibliography have been assessed and recalibrated. New expressions have been proposed that allow obtaining hourly values of ultraviolet radiation from global radiation measures and parameters as clearness index and relative optical air mass. The accuracy of these models has been assessed through the following statistical indices: mean bias, mean-absolute bias and root-mean-square errors whose values are close to zero, below 7% and below 10%, respectively. Two new clear sky models have been used to evaluate two new parameters: ultraviolet and global cloud modification factors, which can help to understand the role of the clouds on solar radiation. The ultraviolet cloud modification factor depends on cloudiness in such a way that its value under overcast skies is half of the cloudless skies one. Exponential and potential fits are the best relationships between both cloud factors. Finally, these parameters have been used to build new UV empirical models which show low values of the statistical indices mentioned above. Copyright © 2009 Royal Meteorological Society [source] Radiographic lung density assessed by computed tomography is associated with extravascular lung water contentACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 8 2010V. V. KUZKOV Background: We hypothesized that in acute lung injury (ALI), the volume of pulmonary tissue with aqueous density, as determined by spiral computed tomography (CT), is associated with extravascular lung water content. Our aim was to compare tissue volume index, as assessed by CT, before and after oleic acid-induced ALI, with extravascular lung water indexes (EVLWI), determined with single transpulmonary thermodilution (EVLWISTD), thermal-dye dilution (EVLWITDD), and postmortem gravimetry (EVLWIG). Methods: Seven instrumented sheep received an intravenous infusion of oleic acid 0.08 ml/kg (OA group) and four animals had vehicle only (Control group). The day before, and immediately after the experiment, sheep were anesthetized to undergo quantitative CT examinations during a short breath hold. Hemodynamics, oxygenation, EVLWISTD, and EVLWTDD were registered. Linear regression analysis was used to assess the relationships between EVLWISTD, EVLWTDD, EVLWIG, and lung tissue volume index (TVICT) determined with CT. Results: In the OA group, total lung volume increased compared with Controls. Poorly and non-aerated lung volumes increased a 3.6- and 4.9-fold, respectively, and TVICT almost doubled. EVLWISTD, EVLWITDD, and TVICT were associated significantly with EVLWIG (r=0.85, 0.90, and 0.88, respectively; P<0.001). TVICT deviated from the reference EVLWIG values to the greatest extent with a mean bias ± 2SD of 4.0 ± 6.0 ml/kg. Conclusions: In ovine oleic acid-induced ALI, lung tissue volume, as assessed by quantitative CT, is in close agreement with EVLWI, as determined by indicator dilution methods and postmortem gravimetry, but overestimates lung fluid content. [source] A near-infrared method for the assay of cineole in eucalyptus oil as an alternative to the official BP methodJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 1 2001Nicola D. Wilson Eucalyptus oil of British Pharmacopoeia (BP) and European Pharmacopoeia standard must contain not less than 70.0% w/w 1,8-cineole (eucalyptol). The official assay is a freezing-point method which involves the addition of o -cresol to the eucalyptus oil, whereupon the o -cresol and the 1,8-cineole form a solid complex. The assay has several disadvantages and we aim to show that near-infrared (NIR) spectroscopy is an attractive alternative to this method, in that it is simple to use, requires no sample preparation and is potentially as accurate as the traditional method. Thirty different eucalyptus oil samples were scanned on the FOSS NIRSystems 6500 Rapid Content Sampler using a reflectance vessel as sample presentation method. The cineole content of each sample was determined by the BP method and these reference data were used to construct two calibration equations for cineole content in the oils using Vision software. The mean accuracy for the NIR method differed by 1.01% or less, and the mean bias by ±0.33% or less, compared with the BP method. Calculation of the 95% confidence intervals for the slope and intercept of plots of NIR predicted values against BP method reference values showed that there was no evidence of fixed or relative systematic errors. Tests for short-term and intermediate repeatability were conducted. The standard deviation was 0.83% w/w or less and the coefficient of variation was 1.11% or less. The confidence intervals for both short-term and intermediate repeatability overlapped with that for the BP method, suggesting that there was no evidence for a difference in values obtained by the BP and NIR methods. The range of cineole contents used in the calibrations was extended by incorporating five samples of eucalyptus oil spiked with cineole, and five samples of two essential oils known to have a lower cineole content than eucalyptus oil, to give a range of 52.5 to 99.0% w/w. The mean accuracy decreased to an error of 1.26% or less and the bias to ±0.50% or less. Again, confidence intervals suggested there was no evidence for fixed or systematic errors in the NIR calibrations. We propose that NIR spectroscopy could be used as an alternative method for the determination of cineole content in eucalyptus oils. [source] Models for potentially biased evidence in meta-analysis using empirically based priorsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2009N. J. Welton Summary., We present models for the combined analysis of evidence from randomized controlled trials categorized as being at either low or high risk of bias due to a flaw in their conduct. We formulate a bias model that incorporates between-study and between-meta-analysis heterogeneity in bias, and uncertainty in overall mean bias. We obtain algebraic expressions for the posterior distribution of the bias-adjusted treatment effect, which provide limiting values for the information that can be obtained from studies at high risk of bias. The parameters of the bias model can be estimated from collections of previously published meta-analyses. We explore alternative models for such data, and alternative methods for introducing prior information on the bias parameters into a new meta-analysis. Results from an illustrative example show that the bias-adjusted treatment effect estimates are sensitive to the way in which the meta-epidemiological data are modelled, but that using point estimates for bias parameters provides an adequate approximation to using a full joint prior distribution. A sensitivity analysis shows that the gain in precision from including studies at high risk of bias is likely to be low, however numerous or large their size, and that little is gained by incorporating such studies, unless the information from studies at low risk of bias is limited. We discuss approaches that might increase the value of including studies at high risk of bias, and the acceptability of the methods in the evaluation of health care interventions. [source] Reliability of a new ultrasonic cardiac output monitor in recipients of living donor liver transplantation,,§¶LIVER TRANSPLANTATION, Issue 7 2008Bai-Chuan Su The ultrasonic cardiac output monitor (USCOM) is a new Doppler device for noninvasive hemodynamic monitoring. The aim of this prospective nonrandomized study was to test the feasibility, perioperative reliability, and clinical applicability of using USCOM as an alternative to pulmonary artery catheterization in recipients of living donor liver transplantation. Thirteen patients scheduled to receive living donor liver transplants were initially recruited. Three were subsequently excluded prior to the commencement of surgery because of technical difficulties in obtaining diagnostic-quality images with USCOM. Ten patients proceeded to be studied. Cardiac output measurements by thermodilution and USCOM were compared at 30-minute intervals throughout the procedure and at 10 specific procedural reference points during the surgery when hemodynamic changes were most likely to be observed. The data were analyzed with Lin's concordance coefficient and Bland-Altman analysis. Two hundred ninety paired cardiac output values were obtained from the 10 patients. The concordance between both methods was excellent in 8 patients and satisfactory in 2. Bland-Altman analysis of all data produced a mean bias of , 0.02 L/minute for USCOM, and the 95% limits of agreement were ,1.06 to +1.10 L/minute. Further analysis of the 10 reference time points showed minimal bias and high levels of agreement between the methods. We conclude that USCOM provides an accurate and noninvasive method for cardiac output measurement during liver transplantation. It may therefore represent an alternative to pulmonary artery catheter placement with consequent reduction in patient's risk and morbidity associated with catheterization. Liver Transpl 14:1029,1037, 2008. © 2008 AASLD. [source] Utility of pulse oximetry in the detection of arterial hypoxemia in liver transplant candidatesLIVER TRANSPLANTATION, Issue 4 2002Gary A. Abrams MD Assistant Professor of Medicine Hepatopulmonary syndrome, arterial hypoxemia caused by intrapulmonary vasodilatation, occurs in approximately 10% of patients with cirrhosis. The severity of hypoxemia affects liver transplant candidacy and is associated with increased morbidity and mortality posttransplantation. Screening guidelines for detecting the presence of arterial hypoxemia do not exist. The aim of this study is to investigate the accuracy and utility of pulse oximetry in the detection of hypoxemia (PaO2 < 70 mm Hg) in patients with cirrhosis. Two hundred prospective liver transplant candidates were compared with 94 controls. Arterial oxyhemoglobin saturation was obtained by pulse oximetry (SpO2) and compared with simultaneous arterial blood gas (ABG) oxyhemoglobin values (SaO2; bias = the difference). PaO2, carboxyhemoglobin, methemoglobin, and routine clinical and biochemical parameters were investigated to account for the bias. SpO2 overestimated SaO2 in 98% of patients with cirrhosis (mean bias, 3.37%; range, ,1% to 10%). Forty-four percent of patients with cirrhosis and controls had a bias of 4% or greater. No clinical or biochemical parameters of cirrhosis accounted for the overestimation of pulse oximetry. Twenty-five subjects with cirrhosis were hypoxemic, and an SpO2 of 97% or less showed a sensitivity of 96% and a positive likelihood ratio of 3.9 for detecting hypoxemia. An SpO2 of 94% or less detected all subjects with an arterial PaO2 less than 60 mm Hg. Pulse oximetry significantly overestimates arterial oxygenation, and the inaccuracy is not influenced by liver disease. Nevertheless, pulse oximetry can be a useful screening tool to detect arterial hypoxemia in patients with cirrhosis, but a higher threshold for obtaining an ABG must be used. [source] Comparison of different near-infrared spectroscopic cerebral oxygenation indices with central venous and jugular venous oxygenation saturation in childrenPEDIATRIC ANESTHESIA, Issue 2 2008NICOLE NAGDYMAN Summary Background:, We compared two different near-infrared spectrophotometers: cerebral tissue oxygenation index (TOI) measured by NIRO 200 and regional cerebral oxygenation index (rSO2) measured by INVOS 5100 with venous oxygen saturation in the jugular bulb (SjO2) and central SvO2 from the superior caval vein (SVC) during elective cardiac catheterization in children. Methods:, A prospective observational clinical study in 31 children with congenital heart defects in a catheterization laboratory was undertaken. TOI was compared with SjO2 in the left jugular bulb and with SvO2. rSO2 was compared with SjO2 from the right jugular bulb and SvO2. Linear regression analysis and Pearson's correlation coefficient were calculated and Bland,Altman analyses were performed. Results:, Cerebral TOI and SjO2 were significantly correlated (r = 0.56, P < 0.0001), as well as TOI and SvO2 with r = 0.74 (P < 0.0001). Bland,Altman plots showed a mean bias of ,4.3% with limits of agreement of 15.7% and ,24.3% for TOI and SjO2 and a mean bias of ,4.9% with limits of agreement of 10.3% and ,20.1% for TOI and SvO2. Cerebral rSO2 and SjO2 showed a significant correlation (r = 0.83, P < 0.0001) and rSO2 and SvO2 showed excellent correlation with r = 0.93 (P < 0.0001). Bland,Altman plots showed a mean bias of ,5.2% with limits of agreement of between 8.4% and ,18.8% for rSO2 and SjO2 and a mean bias of 5.6% with limits of agreement of 13.4% and ,2.2% for rSO2 and SvO2. Conclusions:, Both near-infrared spectroscopy devices demonstrate a significant correlation with SjO2 and SvO2 values; nevertheless both devices demonstrate a substantial bias of the measurements to both SjO2 and SvO2. [source] 2352: The influence of central corneal thickness and corneal biomechanics in glaucomaACTA OPHTHALMOLOGICA, Issue 2010FC LAM Purpose To look at the impact that central corneal thickness and corneal biomechanics can have on intraocular pressure (IOP) measurements and their effect on visual fields. Methods Written and informed consent from patients and guidance from the local research ethics committee was obtained. Ocular diagnoses and ocular medications were recorded. IOPs were recorded using Goldmann applanation tonometry (GAT)followed by dynamic contour tonometry with the Pascal tonometer. Central corneal thickness(CCT) was measured using ultrasound. Visual fields were recorded using Humphries perimetry. Bland-Altman plots were used to compare the 2 methods. Results 92 eyes of 46 patients were included. Median CCT 556µm(range:427µm-634µm). Despite a good correlation of the IOP measurements usin the two different techniques(r=0.7; p< 0.01), there was a significant difference in limits of agreement(LOA) of DCT to GAT on the Bland-Altman analysis. The LOA was 8.6mmHg to -4.8mmHg with a mean bias of 1.9mmHg. This persisted even after correction for CCT. Ocular hypertensives had a wider LOA than glaucoma patients. Conclusion DCT IOP measurements can be significantly different from GAT IOPs even after taking into account central corneal thickness. Compared to CCT, corneal hysteresis appears to have a greater impact on IOP measurements. This could have important prognostic implications. [source] Failed Validation of the Argall Weight Formula for Estimating Children's Weight in an Australian Emergency DepartmentACADEMIC EMERGENCY MEDICINE, Issue 5 2007Kevin Nguyen BackgroundAn estimate of a child's weight is required for critical interventions, particularly pharmacotherapy. Weight measurement is not always practical, so weight estimation methods are used. Recently, a new weight estimation formula was suggested. The Argall formula estimates weight in kilograms as follows: (age in years + 2) × 3. ObjectivesTo validate the Argall weight formula. MethodsThis was a prospective, observational, cohort study conducted in the pediatric emergency department (ED) of Sunshine Hospital. Children aged up to 11 years who presented to the ED during August 18, 2005, to February 25, 2006, were included. Actual weight, height, age, and ethnicity were obtained. Data were analyzed by descriptive statistics (proportion, mean, median, and SD). Agreement between estimated weight using the Argall formula and measured weight is reported by using mean bias, SD, and root mean square error (RMSE) analysis. ResultsFour hundred ten cases were included, 46% were female, and the median age was 4 years. The Argall formula had a mean bias of ,1.66 kg and RMSE of 5.65. Only 37% of Argall estimates were within 10% of the child's actual weight. The formula performed less well in children weighing more than 35 kg but performed better in Asian children than white children. ConclusionsThe Argall weight estimation formula has poor accuracy for weight estimation in Australian children, in particular those weighing more than 35 kg. [source] | ||||||||||