Browsing by Browse by FOR 2008 "010402 Biostatistics"

Pharmacy and therapeutics committees commonly cite a lack of generalizability as a reason for not incorporating cost-effectiveness information into decision making. To address this concern, many committees undertake site-specific economic evaluations, which are often limited by small sample sizes and non-randomized designs. We show how 2 complementary approaches were used to minimize these limitations in an economic evaluation of abciximab at 1 institution. Using a propensity score methodology, we selected patients who did not receive abciximab for the comparison cohort. Then, we adopted a Bayesian, hierarchical, random-effects model to integrate site-specific and clinical trial data. We applied the posterior distributions of effectiveness with local cost data in a traditional decision-analytic model. In 74% of the simulations, abciximab was cost-effective at 1 institution at the $50,000 per life year saved threshold, assuming a 50:50 split of patients undergoing coronary stenting and angioplasty. Among patients undergoing coronary stenting, the cost-effectiveness ratio of the addition of abciximab was at or below the $50,000 per life year saved threshold in 66.0% of the simulations.

In this paper it is demonstrated how the Bayesian parametric bootstrap can be adapted to models with intractable likelihoods. The approach is most appealing when the computationally efficient semi-automatic approximate Bayesian computation (ABC) summary statistics are selected. The parametric bootstrap approximation is used to form a proposal distribution in ABC algorithms to improve the computational efficiency. The new approach is demonstrated through the sequential Monte Carlo and the ABC importance and rejection sampling algorithms. We found efficiency gains in two simulation studies, the univariate g-and-k quantile distribution, a toggle switch model in dynamic bionetworks, and in a stochastic model describing expanding melanoma cell colonies.

The circulating concentrations of progesterone, FSH, and follistatinacross the estrous cycle and gestation were compared inAustralian merino sheep that were homozygous for the Booroolagene, FecB, or were noncarriers. The Booroola phenotype is dueto a point mutation in the bone morphogenetic protein receptor1B. Progesterone concentrations began to rise earlier and werehigher in the Booroola ewes than in the noncarriers on mostdays of the luteal phase but not during the follicular phase ofthe cycle. Follistatin concentrations remained unchanged acrossthe estrous cycle in both groups of ewes, with no differencesbetween genotypes. FSH concentrations were higher in Booroolaewes than in noncarrier ewes on most days of the estrouscycle, with a significantly higher and broader peak of FSHaround the time of estrus. Progesterone concentrations were significantlyhigher in early and midgestation in Booroola ewes butwere lower toward the end of gestation than those in noncarriers.FSH declined in both groups across gestation, with lowerconcentrations of FSH in Booroola ewes during midgestation.Follistatin remained unchanged across gestation in Booroolaewes and noncarrier ewes with a twin pregnancy but declinedacross gestation in noncarrier ewes with a singleton pregnancy.These results suggest that follistatin concentration is not regulatedby the FecB gene during the estrous cycle and pregnancybut is influenced by the number of fetuses. However, the FecBgene appears to positively affect both progesterone and FSHduring the estrous cycle and across pregnancy, which suggeststhat bone morphogenetic proteins play an important role in theregulation of both hormones.

We conducted a prospective study of an electronic clinical reminder system in an academic medical center-based human immunodeficiency virus (HIV) specialty clinic. Published performance indicators were used to examine adherence to HIV practice guidelines before and after its implementation for 1204 patients. More than 90% of patients received CD₄ cell count and HIV type 1 (HIV-1) RNA level monitoring every 3-6 months during both time periods, and ~80% of patients with a CD₄ cell count nadir of <350 cells/mm³ received highly active antiretroviral therapy. Patients were significantly more likely to receive prophylaxis against 'Mycobacterium avium' complex (hazard ratio, 3.84; 95% confidence interval [CI], 1.58-9.31; 'P'=.003), to undergo annual cervical carcinoma screening (OR, 2.09; 95% CI, 1.04-4.16; 'P'=.04), and to undergo serological screening for Toxoplasma gondii (odds ratio [OR], 1.86; 95% CI, 1.05-3.27; 'P'=.03) and syphilis infection (OR, 3.71; 95% CI, 2.37-5.81; 'P'<.0001). HIV clinical reminders delivered at the time that HIV care is provided were associated with more timely initiation of recommended practices.

Background: Speech pathologists infrequently address the quality of aphasic people's lives in a direct manner in rehabilitation, most likely due to the difficulty in grasping the role of communication in quality of life (QOL). Despite considerable research into aphasic language impairments and communication disabilities, there is no clear evidence how aphasia impacts on clients' QOL. This paper reports on a comprehensive evaluation of 30 people with mild to moderate aphasia to determine which aspects of communication predict their QOL. A conceptual model of the relationship between communication and QOL was devised, using the disablement framework of the International Classification of Impairment, Activity and Participation Beta-2 Draft (ICIDH-2) (World Health Organisation, 1998). Communication was conceptualised as language impairment, functional communication ability and activity, and social participation. QOL included both health-related QOL (HRQOL) and psychological well-being concepts. Aims: The aim of this study was to investigate how measures of impairment, activity and participation, and measures of QOL related to each other for people with aphasia, for the purpose of: (1) determining which specific communication assessments were most predictive of their QOL; and (2) determining whether HRQOL or psychological well-being was represented more in relationships, thus indicating a focus for QOL in aphasia. Methods & Procedures: Thirty people aged 57-88 years (mean = 70.7yrs) with predominantly mild to moderate chronic aphasia (mean WAB AQ = 74.4, range 21.9-5.8; mean TPO = 41 mths, range 10-108 mths) participated in this study. In total, 13 standardised and specifically designed measures evaluated the different concepts of the model. Maximal multiple regression analysis illustrated which communication measures were most predictive of participants' HRQOL and psychological well-being. Outcomes & Results: Overall, aphasic people's communication predicted their psychological well-being and social health (a subscale of HRQOL). Specifically, the findings demonstrated that functional communication ability, and language functioning to a lesser degree, were implicated in QOL, providing evidence for particular speech pathology interventions in addressing clients' QOL. Finally, emotional health powerfully influenced the relationships among variables, and physiological/physical health was a determinant of social participation.

This dataset consists of scripts developed for the research project A Framework for Optimizing Breeding Pairs Using Artificial Intelligence. The scripts are for simulations (in .py format) for each of the chapters, along with results (in .py or .xlsx format). These data and results were generated through simulations, and all results and metadata can be obtained by running the simulation scripts. The scripts have been organized based on chapters, and are simulation scripts that become the basis of this research. Raw metadata from which the results reported in the thesis were based upon can be requested on demand.

The efficacy of a traditional Chinese medicine medication derives from the complex interactions of herbs or Chinese Materia Medica in a formula. The aim of this paper is to propose a new approach to systematically generate combinations of interacting herbs that might lead to good outcome. Our approach was tested on a data set of prescriptions for diabetic patients to verify the effectiveness of detected combinations of herbs. This approach is able to detect effective higher orders of herb-herb interactions with statistical validation. We present an exploratory analysis of clinical records using a pattern mining approach called Interaction Rules Mining.

Although adherence to HAART at a level above 95% has been associated with optimal viral suppression, the impact of different levels of adherence on long-term clinical outcomes has not been determined. We used an objective pharmacy-based measure to examine the association between three levels of adherence to HAART and disease progression among a population-based cohort of HIV-infected patients attending an urban HIV specialty clinic. Higher levels of adherence to HAART were significantly associated with longer time to virologic failure (P<50.001), greater increase in CD4 cell count (P=0.04), and lower risk of progression to clinical AIDS or death (P<0.007). After controlling for other factors, patients with low adherence had over five times the risk of disease progression than patients with moderate adherence (P=0.007) or patients with high adherence (P=0.001). There was no significant difference in the risk of progression between patients with moderate and high levels of adherence (P>0.2). Patients who progressed to AIDS or death had significantly higher viral loads (P¼0.01) and lower CD4 cell counts (P=0.03) than patients who experienced virologic failure, but did not progress.

OBJECTIVE: It has been shown that greater physician experience in the care of persons with AIDS prolongs survival, but how more experienced primary care physicians achieve better outcomes is not known. DESIGN/SETTING/PATIENTS: Retrospective cohort study of HIV-infected patients enrolled in a large staff-model health maintenance organization from 1990 through 1999. MEASUREMENTS: Adjusted odds of medical service delivery and adjusted hazard ratio of death by physician experience level (least, moderate, most) and service utilization. MAIN RESULTS: Primary care delivery by physicians with greater AIDS experience was associated with improved survival. After controlling for disease severity, patients cared for by the most experienced physicians were twice as likely to receive a primary care visit in a given month compared with patients of the least and moderately experienced physicians (P<.01). Patients of the least experienced physicians received the lowest level of outpatient pharmacy and laboratory services (P<.001) and were half as likely to have a specialty care visit compared with patients of the most and moderately experienced physicians (P<.05). Patients who received infrequent primary care visits by the least experienced physicians were 15.3 times more likely to die than patients of the most experienced physicians (P=.02). There was a significant increase in primary care services delivered to the population of HIV-infected patients receiving care in 1999, when highly active antiretroviral therapy (HAART) was in general use, compared with the time period prior to the introduction of HAART. CONCLUSIONS: Primary care delivery by physicians with greater HIV experience contributes to improved patient outcomes.

Inclusion body hepatitis caused by Fowl adenovirus is an important disease of chickens. A major risk factor identified in this thesis was multi-age sites. Viral load, faecal shedding of virus, clinical signs and bursal atrophy were reduced in chickens carrying maternal antibody or those infected at 14-17 days of age relative to 1-3 days of age. Methods to quantify FAdV-8b in litter and dust were developed and the utility of these tests shown. Presence of high levels in litter darkling beetles is suggestive of a role in epidemiology. FAdV8 was readily inactivated in litter at temperatures of 45˚C or above.

Measurement of health-related quality-of-life (HRQL) captures dimensions of health not otherwise assessed. However, HRQL measurement is time-consuming and difficult to incorporate into a routine clinical care setting. The purpose of this study was to assess the construct validity, discriminative ability, and feasibility of administering a single-item health status measure (EVGGFP) of HRQL rating health as excellent, very good, good, fair, or poor among HIV-infected patients in routine clinical care. Patients attending an urban HIV specialty clinic completed a survey assessing their current symptom burden, HRQL as measured by EVGGFP and by a 7-domain, 21-item HRQL instrument (HRQL-21), and sociodemographic factors ('n' = 269). Patients were predominantly men (91%), 27% reported a history of intravenous drug use, and over half had some college education. We used multiple regression analysis to examine the association between HRQL assessed by EVGGFP and the HRQL-21. We compared the discriminative ability of EVGGFP and the HRQL-21 to detect differences in CD4 cell count, plasma HIV-1 RNA level, and symptom burden. We found that HRQL scores determined by EVGGFP were significantly associated with domain scores from the HRQL-21 (adjusted R² 0.42-0.69). The discriminative ability of EVGGFP was equivalent to that of the HRQL-21. EVGGFP had high sensitivity and low to moderate specificity in identifying patients with poor overall HRQL who might benefit from more comprehensive evaluation of multiple HRQL domains. EVGGFP can be used to assess health status among HIV-infected patients in routine clinical care and may be useful in settings in which comprehensive HRQL assessment is not practical.

The quality of RNA samples and slide hybridizations are paramount for gene expression studies. Here the focus is on hybridization quality in Affymetrix arrays and a comparison of the results of differential expression analysis for six summarization methods using slides of good and bad quality. The overlap of probes detected as differentially expressed across methods is very small even with good arrays. Slides of inferior quality also significantly change the generated list of differentially expressed genes. Extensive qualitative and quantitative quality control measures should be used prior to downstream analyses of data to ensure early detection and removal of problematic slides. Given the high variability of results across summarization methods it is recommended that different methods are used to conduct analyses and the intersecting results of these are used for further downstream analyses.