PS-SiZer map to investigate significant features of body-weight profile changes in HIV infected patients in the IeDEA Collaboration

Objectives: We extend the method of Significant Zero Crossings of Derivatives (SiZer) to address within-subject correlations of repeatedly collected longitudinal biomarker data and the computational aspects of the methodology when analyzing massive biomarker databases. SiZer is a powerful visualization tool for exploring structures in curves by mapping areas where the first derivative is increasing, decreasing or does not change (plateau) thus exploring changes and normalization of biomarkers in the presence of therapy. Methods: We propose a penalized spline SiZer (PS-SiZer) which can be expressed as a linear mixed model of the longitudinal biomarker process to account for irregularly collected data and within-subject correlations. Through simulations we show how sensitive PS-SiZer is in detecting existing features in longitudinal data versus existing versions of SiZer. In a real-world data analysis PS-SiZer maps are used to map areas where the first derivative of weight change after antiretroviral therapy (ART) start is significantly increasing, decreasing or does not change, thus exploring the durability of weight increase after the start of therapy. We use weight data repeatedly collected from persons living with HIV initiating ART in five regions in the International Epidemiologic Databases to Evaluate AIDS (IeDEA) worldwide collaboration and compare the durability of weight gain between ART regimens containing and not containing the drug stavudine (d4T), which has been associated with shorter durability of weight gain. Results: Through simulations we show that the PS-SiZer is more accurate in detecting relevant features in longitudinal data than existing SiZer variants such as the local linear smoother (LL) SiZer and the SiZer with smoothing splines (SS-SiZer). In the illustration we include data from 185,010 persons living with HIV who started ART with a d4T (53.1%) versus non-d4T (46.9%) containing regimen. The largest difference in durability of weight gain identified by the SiZer maps was observed in Southern Africa where weight gain in patients treated with d4T-containing regimens lasted 59.9 weeks compared to 133.8 weeks for those with non-d4T-containing regimens. In the other regions, persons receiving d4T-containing regimens experienced weight gains lasting 38-62 weeks versus 55-93 weeks in those receiving non-d4T-based regimens. Discussion: PS-SiZer, a SiZer variant, can handle irregularly collected longitudinal data and within-subject correlations and is sensitive in detecting even subtle features in biomarker curves

Effects of tobacco use on non-adherence to antiretroviral therapy among HIV-positive patients in South Africa

This study aimed to estimate the relationship between tobacco use and non-adherence to antiretroviral therapy (ART) in a South African sample. Participants were 1 963 HIV patients who attended a primary care clinic in Pretoria (female = 68.5%; black African = 99.5%; median age = 37.0 years; tobacco users only = 8.6%, problem drinkers only = 14.9%, and tobacco users and problem drinkers = 10.5%). In adjusted logistic regression analysis, tobacco use only was not significantly associated with non-adherence to ART. Alcohol use only (OR: 1.72; CI: 1.26, 2.36) and tobacco use and problem drinking (OR: 2.31; CI: 1.60, 3.33) were highly associated with non-adherence to ART

National guidelines not always followed when diagnosing smear-negative pulmonary tuberculosis in patients with HIV in Botswana.

BACKGROUND: Diagnosis of smear negative pulmonary tuberculosis (SNPTB) is challenging, especially in patients with HIV. The Botswana National Tuberculosis Program (BNTP) guidelines give guidance in diagnosing and treating SNPTB. Patients with chronic cough should be screened for TB by 3 sputum smear investigations. If negative, a chest x-ray (CXR) should be performed. If negative for TB, antimicrobial treatment for other infections should be started. We investigated the clinicians' use of the guidelines in clinical practice. METHODS: Data regarding the medical history (coughing period), requested and conducted investigations concerning tuberculosis diagnosis (sputum smear or culture or CXR) or alternative diagnoses (sputum microscopy or blood or sputum culture for diagnosis of other organisms), in SNPTB HIV-positive patients (outpatients and admitted patients) from 2006-2009 in a district hospital in Botswana were extracted from all available hospital medical records. Additionally, a survey was done in all doctors diagnosing SNPTB in this hospital using a self-administered questionnaire with questions regarding the application of the BNTP guidelines in practice. Descriptive analyses of collected data were performed to test the compliance to the guidelines. RESULTS: Data from medical records showed that in 47.0% (132/281) of patients, TB treatment was started without microbiological results from sputum smears. Other methods to rule out or confirm PTB were used in 2.1% (6/281); and 99.6% (280/281) of SNPTB patients had received a CXR. The survey in 7 clinicians found that all always used CXR, and all clinicians requested three sputum results only sometimes. Six out of 7 clinicians started antibiotics before starting TB treatment. Reasons clinicians gave for difficulties in following the guidelines included inability of patients to produce sputum; and laboratory delays in releasing sputum results. CONCLUSION: Between 2006 and 2009 a high proportion of SNPTB diagnoses in a district hospital in Botswana were not supported by laboratory investigation

Nutritional Supplementation in HIV‐Infected Individuals Can Be Beneficial in Certain Patient Groups

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