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Duke University Medical Center (duke + university_medical_center)
Selected AbstractsCoping With Missing Attribute Values Based on Closest Fit in Preterm Birth Data: A Rough Set ApproachCOMPUTATIONAL INTELLIGENCE, Issue 3 2001Jerzy W. Grzymala-Busse Data mining is frequently applied to data sets with missing attribute values. A new approach to missing attribute values, called closest fit, is introduced in this paper. In this approach, for a given case (example) with a missing attribute value we search for another case that is as similar as possible to the given case. Cases can be considered as vectors of attribute values. The search is for the case that has as many as possible identical attribute values for symbolic attributes, or as the smallest possible value differences for numerical attributes. There are two possible ways to conduct a search: within the same class (concept) as the case with the missing attribute values, or for the entire set of all cases. For comparison, we also experimented with another approach to missing attribute values, where the missing values are replaced by the most common value of the attribute for symbolic attributes or by the average value for numerical attributes. All algorithms were implemented in the system OOMIS. Our experiments were performed on the preterm birth data sets provided by the Duke University Medical Center. [source] Risk Factors for Surgical Site Infections in Older PeopleJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 3 2006Keith S. Kaye MD OBJECTIVES: To identify risk factors for surgical site infection (SSI) in older people and to test a priori hypotheses regarding particular variables and SSI risk. DESIGN: Case-control study. SETTING: Duke University Medical Center and seven community hospitals in North Carolina and Virginia. PARTICIPANTS: Elderly patients (,65) who underwent surgery between 1991 and 2002 at the study hospitals. Cases were elderly patients with SSI; controls were elderly operative patients without SSI. Infection control practitioners prospectively identified patients. MEASUREMENTS: Data were collected retrospectively. Case patients who developed SSI were compared with control patients who did not develop SSI. RESULTS: Five hundred sixty-nine SSI cases were identified, and 589 uninfected controls were selected. In multivariate analysis, independent predictors of SSI included obesity (odds ratio (OR)=1.77, 95% confidence interval (CI)=1.34,2.32), chronic obstructive pulmonary disease (COPD) (OR=1.66, 95% CI=1.17,2.34), and a wound class classified as contaminated or dirty (OR=1.65, 95% CI=1.01,2.72). Having private insurance was associated with lower risk (OR=0.29, 95% CI=0.12,0.68). CONCLUSION: This study identified several independent predictors of SSI in older people, including comorbid conditions (COPD and obesity), perioperative variables (wound class), and socioeconomic factors (private insurance, which was associated with lower risk). The results from this study can be used to design and implement interventions for SSI prevention in high-risk older people. [source] Issues facing clinical trials of the futureJOURNAL OF INTERNAL MEDICINE, Issue 5 2003R. M. Califf Abstract. Califf RM (Duke University Medical Center, Durham, NC, USA). Issues facing clinical trials of the future (Clinical Trials). J Intern Med 2003; 254: 426,433. Diagnostic and therapeutic technology continues to advance rapidly, as does our knowledge of therapeutics and of clinical research methods. Unfortunately, these advances have been only poorly coupled with our knowledge of therapeutic principles, leading to increasing uncertainty about which technologies are truly effective and, amongst those that are effective, which are most effective for the cost. This article presents general principles derived from several investigators' experiences with clinical trials, and uses them to suggest how future clinical trials may differ from current approaches. A proposed organization for future trials also is elucidated. [source] Herpes zoster in older adults. (Duke University Medical Center, Durham, NC) Clinical Infectious Diseases.PAIN PRACTICE, Issue 4 20011486., 2001;32:148 Herpes zoster (HZ) strikes millions of older adults annually worldwide and disables a substantial number of them via postherpetic neuralgia (PHN). Key aged-related clinical, epidemiological, and treatment features of zoster and PHN are reviewed in this article. HZ is caused by renewed replication and spread of the varicella-zoster virus (VZV) in sensory ganglia and afferent peripheral nerves in the setting of age-related, disease-related, and drug-related decline in cellular immunity to VZV. VZV-induced neuronal destruction and inflammation causes the principal problems of pain, interference with activities in daily living, and reduced quality of life in elderly patients. Recently, attempts to reduce or eliminate HZ pain have been bolstered by the findings of clinical trials that antiviral agents and corticosteroids are effective treatment for HZ and that tricyclic antidepressants, topical lidocaine, gabapentin, and opiates are effective treatment for PHN. Although these advances have helped, PHN remains a difficult condition to prevent and treat in many elderly patients. Comment by Miles Day, M.D. This article reviews the epidemiology clinical features diagnosis and treatment of acute herpes zoster. It also describes the treatment of postherpetic neuralgia. While this is a good review for the primary care physician, the discussion for the treatment for both acute herpes zoster and postherpetic neuralgia do not mention invasive therapy. It is well documented in pain literature that sympathetic blocks with local anesthetic and steroid as well as subcutaneous infiltration of active zoster lesions not only facilitate the healing of acute herpes zoster but also prevents or helps decrease the incidence of postherpetic neuralgia. All patients who present to the primary care physician with acute herpes zoster should have an immediate referral to a pain management physician for invasive therapy. The treatment of postherpetic neuralgia is a challenging experience both for the patient and the physician. While the treatments that have been discussed in this article are important, other treatments are also available. Regional nerve blocks including intercostal nerve blocks, root sleeve injections, and sympathetic blocks have been used in the past to treat postherpetic neuralgia. If these blocks are helpful, one can proceed with doing crynourlysis of the affected nerves or also radio-frequency lesioning. Spinal cord stimulation has also been used for those patients who are refractory to noninvasive and invasive therapy. While intrathecal methylprednisolone was shown to be effective in the study quoted in this article one must be cautious not to do multiple intrathecal steroid injections in these patients. Multilple intrathecal steroid injections can lead to archnoiditis secondary to the accumulation of the steroid on the nerve roots and in turn causing worsening pain. [source] Cardiopulmonary complications leading to premature deaths in adult patients with sickle cell diseaseAMERICAN JOURNAL OF HEMATOLOGY, Issue 1 2010Courtney D. Fitzhugh Sickle cell disease (SCD) is associated with early mortality. We sought to determine the incidence, cause, and risk factors for death in an adult population of patients with SCD. All patients aged ,18 years seen at the Adult Sickle Cell Center at Duke University Medical Center between January 2000 and April 2005 were enrolled. Forty-three patients (21 males and 22 females) died during the study period. The median age of survival was 39 years for females (95% CI: 34,56), 40 years for males (95% CI: 34,48), and 40 years overall (95% CI: 35,48). Cardiac causes of death accounted for 25.6% (11/43 patients); pulmonary, 14.0% (six patients); other SCD related, 32.6% (14 patients); unknown, 14.0% (six patients); and others, 14.0% (six patients). Pulseless electrical activity arrest, pulmonary emboli, multiorgan failure, and stroke were the most frequent causes of death. Among the deceased patients, the most common premorbid conditions were cardiopulmonary: acute chest syndrome/pneumonia (58.1%), Pulmonary hypertension (pHTN; 41.9%), systemic HTN (25.6%), congestive heart failure (25.6%), myocardial infarction (20.9%), and arrhythmias (14.0%). Tricuspid regurgitant jet velocity was significantly higher (3.1 m/sec vs. 2.6 m/sec, P < 0.001) and hemoglobin significantly lower (8.3 g/dL vs. 9.2 g/dL, P < 0.05) in deceased patients when compared with patients who lived, respectively. With improved preventive and therapeutic advances, including hydroxyurea therapy, acute complications such as infection are no longer the leading cause of death; instead, causes of death and premorbid conditions are shifting to chronic cardiopulmonary complications. Further, arrhythmia leading to premature death is under-recognized in SCD and warrants further investigation. Am. J. Hematol., 2010. © 2009 Wiley-Liss, Inc. [source] A Generalized Estimator of the Attributable Benefit of an Optimal Treatment RegimeBIOMETRICS, Issue 2 2010Jason Brinkley Summary For many diseases where there are several treatment options often there is no consensus on the best treatment to give individual patients. In such cases, it may be necessary to define a strategy for treatment assignment; that is, an algorithm that dictates the treatment an individual should receive based on their measured characteristics. Such a strategy or algorithm is also referred to as a treatment regime. The optimal treatment regime is the strategy that would provide the most public health benefit by minimizing as many poor outcomes as possible. Using a measure that is a generalization of attributable risk (AR) and notions of potential outcomes, we derive an estimator for the proportion of events that could have been prevented had the optimal treatment regime been implemented. Traditional AR studies look at the added risk that can be attributed to exposure of some contaminant; here we will instead study the benefit that can be attributed to using the optimal treatment strategy. We will show how regression models can be used to estimate the optimal treatment strategy and the attributable benefit of that strategy. We also derive the large sample properties of this estimator. As a motivating example, we will apply our methods to an observational study of 3856 patients treated at the Duke University Medical Center with prior coronary artery bypass graft surgery and further heart-related problems requiring a catheterization. The patients may be treated with either medical therapy alone or a combination of medical therapy and percutaneous coronary intervention without a general consensus on which is the best treatment for individual patients. [source] Estimating Mean Response as a Function of Treatment Duration in an Observational Study, Where Duration May Be Informatively CensoredBIOMETRICS, Issue 2 2004Brent A. Johnson Summary. After a treatment is found to be effective in a clinical study, attention often focuses on the effect of treatment duration on outcome. Such an analysis facilitates recommendations on the most beneficial treatment duration. In many studies, the treatment duration, within certain limits, is left to the discretion of the investigators. It is often the case that treatment must be terminated prematurely due to an adverse event, in which case a recommended treatment duration is part of a policy that treats patients for a specified length of time or until a treatment-censoring event occurs, whichever comes first. Evaluating mean response for a particular treatment-duration policy from observational data is difficult due to censoring and the fact that it may not be reasonable to assume patients are prognostically similar across all treatment strategies. We propose an estimator for mean response as a function of treatment-duration policy under these conditions. The method uses potential outcomes and embodies assumptions that allow consistent estimation of the mean response. The estimator is evaluated through simulation studies and demonstrated by application to the ESPRIT infusion trial coordinated at Duke University Medical Center. [source] Utilizing Propensity Scores to Estimate Causal Treatment Effects with Censored Time-Lagged DataBIOMETRICS, Issue 4 2001Kevin J. Anstrom Summary. Observational studies frequently are conducted to compare long-term effects of treatments. Without randomization, patients receiving one treatment are not guaranteed to be prognostically comparable to those receiving another treatment. Furthermore, the response of interest may be right-censored because of incomplete follow-up. Statistical methods that do not account for censoring and confounding may lead to biased estimates. This article presents a method for estimating treatment effects in nonrandomized studies with right-censored responses. We review the assumptions required to estimate average causal effects and derive an estimator for comparing two treatments by applying inverse weights to the complete cases. The weights are determined according to the estimated probability of receiving treatment conditional on covariates and the estimated treatment-specific censoring distribution. By utilizing martingale representations, the estimator is shown to be asymptotically normal and an estimator for the asymptotic variance is derived. Simulation results are presented to evaluate the properties of the estimator. These methods are applied to an observational data set of acute coronary syndrome patients from Duke University Medical Center to estimate the effect of a treatment strategy on the mean 5-year medical cost. [source] | ||||||||||