Fitting parametric random effects models in very large data sets with application to VHA national data

<p>Abstract</p> <p>Background</p> <p>With the current focus on personalized medicine, patient/subject level inference is often of key interest in translational research. As a result, random effects models (REM) are becoming popular for patient level inference. However, for very large data sets that are characterized by large sample size, it can be difficult to fit REM using commonly available statistical software such as SAS since they require inordinate amounts of computer time and memory allocations beyond what are available preventing model convergence. For example, in a retrospective cohort study of over 800,000 Veterans with type 2 diabetes with longitudinal data over 5 years, fitting REM via generalized linear mixed modeling using currently available standard procedures in SAS (e.g. PROC GLIMMIX) was very difficult and same problems exist in Stata’s gllamm or R’s lme packages. Thus, this study proposes and assesses the performance of a meta regression approach and makes comparison with methods based on sampling of the full data.</p> <p>Data</p> <p>We use both simulated and real data from a national cohort of Veterans with type 2 diabetes (n=890,394) which was created by linking multiple patient and administrative files resulting in a cohort with longitudinal data collected over 5 years.</p> <p>Methods and results</p> <p>The outcome of interest was mean annual HbA1c measured over a 5 years period. Using this outcome, we compared parameter estimates from the proposed random effects meta regression (REMR) with estimates based on simple random sampling and VISN (Veterans Integrated Service Networks) based stratified sampling of the full data. Our results indicate that REMR provides parameter estimates that are less likely to be biased with tighter confidence intervals when the VISN level estimates are homogenous.</p> <p>Conclusion</p> <p>When the interest is to fit REM in repeated measures data with very large sample size, REMR can be used as a good alternative. It leads to reasonable inference for both Gaussian and non-Gaussian responses if parameter estimates are homogeneous across VISNs.</p

Rationale and design: telepsychology service delivery for depressed elderly veterans

BACKGROUND: Older adults who live in rural areas experience significant disparities in health status and access to mental health care. "Telepsychology," (also referred to as "telepsychiatry," or "telemental health") represents a potential strategy towards addressing this longstanding problem. Older adults may benefit from telepsychology due to its: (1) utility to address existing problematic access to care for rural residents; (2) capacity to reduce stigma associated with traditional mental health care; and (3) utility to overcome significant age-related problems in ambulation and transportation. Moreover, preliminary evidence indicates that telepsychiatry programs are often less expensive for patients, and reduce travel time, travel costs, and time off from work. Thus, telepsychology may provide a cost-efficient solution to access-to-care problems in rural areas. METHODS: We describe an ongoing four-year prospective, randomized clinical trial comparing the effectiveness of an empirically supported treatment for major depressive disorder, Behavioral Activation, delivered either via in-home videoconferencing technology ("Telepsychology") or traditional face-to-face services ("Same-Room"). Our hypothesis is that inhome Telepsychology service delivery will be equally effective as the traditional mode (Same-Room). Two-hundred twenty-four (224) male and female elderly participants will be administered protocol-driven individual Behavioral Activation therapy for depression over an 8-week period; and subjects will be followed for 12-months to ascertain longer-term effects of the treatment on three outcomes domains: (1) clinical outcomes (symptom severity, social functioning); (2) process variables (patient satisfaction, treatment credibility, attendance, adherence, dropout); and (3) economic outcomes (cost and resource use). DISCUSSION: Results from the proposed study will provide important insight into whether telepsychology service delivery is as effective as the traditional mode of service delivery, defined in terms of clinical, process, and economic outcomes, for elderly patients with depression residing in rural areas without adequate access to mental health services. TRIAL REGISTRATION: National Institutes of Health Clinical Trials Registry (ClinicalTrials.gov identifier# NCT00324701)

Relationship Between Vancomycin Trough Concentrations and Nephrotoxicity: A Prospective Multicenter Trial

Several single-center studies have suggested that higher doses of vancomycin, aimed at producing trough concentrations of \u3e15 mg/liter, are associated with increased risk of nephrotoxicity. We prospectively assessed the relative incidence of nephrotoxicity in relation to trough concentration in patients with documented methicillin-resistant Staphylococcus aureus (MRSA) infections at seven hospitals throughout South Carolina. Adult patients receiving vancomycin for at least 72 h with at least one vancomycin trough concentration determined under steady-state conditions were prospectively studied. The relationship between vancomycin trough concentrations of \u3e15 mg/ml and the occurrence of nephrotoxicity was assessed using univariate and multivariate analyses, controlling for age, gender, race, dose, length of therapy, use of other nephrotoxins (including contrast media), intensive care unit (ICU) residence, episodes of hypotension, and comorbidities. Nephrotoxicity was defined as an increase in serum creatinine of 0.5 mg/dl or a ≥ 50% increase from the baseline for two consecutive measurements. MICs of vancomycin for the MRSA isolates were also determined. A total of 288 patients were studied between February 2008 and June 2010, with approximately one-half having initial trough concentrations of ≥ 15 mg/ml. Nephrotoxicity was observed for 42 patients (29.6%) with trough concentrations \u3e15 mg/ml and for 13 (8.9%) with trough concentrations of ≤ 15 mg/ml. Multivariate analysis revealed vancomycin trough concentrations of \u3e15 mg/ml and race (black) as risk factors for nephrotoxicity in this population. Vancomycin trough concentrations of \u3e15 mg/ml appear to be associated with a 3-fold increased risk of nephrotoxicity

Psychosocial Characteristics and Pain Burden of Patients With Suspected Sphincter of Oddi Dysfunction in the EPISOD Multicenter Trial

Patients with several painful functional gastrointestinal disorders (FGIDs) are reported to have a high prevalence of psychosocial disturbance. These aspects have not been studied extensively in patients with suspected Sphincter of Oddi dysfunction (SOD)

Challenges in planning and initiating a randomized clinical study of sphincter of Oddi dysfunction

Sphincter of Oddi dysfunction (SOD) is a controversial topic, especially in patients with no objective findings on laboratory or imaging studies (SOD type III). The value of ERCP manometry with sphincterotomy is unproven and carries significant risks

Effect of Endoscopic Sphincterotomy for Suspected Sphincter of Oddi Dysfunction on Pain-Related Disability Following Cholecystectomy: The EPISOD Randomized Clinical Trial

Abdominal pain after cholecystectomy is common and may be attributed to sphincter of Oddi dysfunction. Management often involves endoscopic retrograde cholangiopancreatography (ERCP) with manometry and sphincterotomy

Can patient and pain characteristics predict manometric sphincter of Oddi dysfunction in patients with clinically suspected sphincter of Oddi dysfunction?

Biliopancreatic-type postcholecystectomy pain, without significant abnormalities on imaging and laboratory test results, has been categorized as “suspected” sphincter of Oddi dysfunction (SOD) type III. Clinical predictors of “manometric” SOD are important to avoid unnecessary ERCP, but are unknown

Southeastern Association of Law Libraries Annual Meeting

The 2009 SEAALL Annual Meeting was held in Athens Georgia, April 16-18, 2009