An algorithm for simulation of a Chemical Transport Equation in an Aquifer

Dynamical systems can be predicted using mathematical models. These models are usually Partial Different Equations (PDEs). Examples include the wave equation, equations for diffusive processes, and the heat conduction equation. Numerical solution of such PDEs describing a given system and its implementation using a suitable computer code can lead to numerous predictions on the dynamical system both in space and time. In this paper, the contaminant / chemical equation and the groundwater flow equation are solved numerically using the Integrated Finite Difference Method (IFDM) and the algorithms generated are simulated using an object oriented code. Generic results generated represent important predications on the fate and transport processes of a chemical in an aquifer   Keywords: Simulation procedure, integrated finite difference method, contaminant equation, discretizatio

Prevalence and correlates of non-disclosure of maternal HIV status to male partners: a national survey in Kenya

Abstract Background Prevention of mother-to-child HIV transmission (PMTCT) programs usually test pregnant women for HIV without involving their partners. Non-disclosure of maternal HIV status to male partners may deter utilization of PMTCT interventions since partners play a pivotal role in decision-making within the home including access to and utilization of health services. Methods Mothers attending routine 6-week and 9-month infant immunizations were enrolled at 141 maternal and child health (MCH) clinics across Kenya from June–December 2013. The current analysis was restricted to mothers with known HIV status who had a current partner. Multivariate logistic regression models adjusted for marital status, relationship length and partner attendance at antenatal care (ANC) were used to determine correlates of HIV non-disclosure among HIV-uninfected and HIV-infected mothers, separately, and to evaluate the relationship of non-disclosure with uptake of PMTCT interventions. All analyses accounted for facility-level clustering, Results Overall, 2522 mothers (86% of total study population) met inclusion criteria, 420 (17%) were HIV-infected. Non-disclosure of HIV results to partners was higher among HIV-infected than HIV-uninfected women (13% versus 3% respectively, p < 0.001). HIV-uninfected mothers were more likely to not disclose their HIV status to male partners if they were unmarried (adjusted odds ratio [aOR] = 3.79, 95% CI: 1.56–9.19, p = 0.004), had low (≤KSH 5000) income (aOR = 1.85, 95% CI: 1.00–3.14, p = 0.050), experienced intimate partner violence (aOR = 3.65, 95% CI: 1.84–7.21, p < 0.001) and if their partner did not attend ANC (aOR = 4.12, 95% CI: 1.89–8.95, p < 0.001). Among HIV-infected women, non-disclosure to male partners was less likely if women had salaried employment (aOR = 0.42, 95%CI: 0.18–0.96, p = 0.039) and each increasing year of relationship length was associated with decreased likelihood of non-disclosure (aOR = 0.90, 95% CI: 0.82–0.98, p = 0.015 for each year increase). HIV-infected women who did not disclose their HIV status to partners were less likely to uptake CD4 testing (aOR = 0.32, 95% CI: 0.15–0.69, p = 0.004), to use antiretrovirals (ARVs) during labor (OR = 0.38, 95% CI 0.15–0.97, p = 0.042), or give their infants ARVs (OR = 0.08, 95% CI 0.02–0.31, p < 0.001). Conclusion HIV-infected women were less likely to disclose their status to partners than HIV-uninfected women. Non-disclosure was associated with lower use of PMTCT services. Facilitating maternal disclosure to male partners may enhance PMTCT uptake

Towards more accurate HIV testing in sub-Saharan Africa: a multi-site evaluation of HIV RDTs and risk factors for false positives

Introduction: Although individual HIV rapid diagnostic tests (RDTs) show good performance in evaluations conducted by WHO, reports from several African countries highlight potentially significant performance issues. Despite widespread use of RDTs for HIV diagnosis in resource-constrained settings, there has been no systematic, head-to-head evaluation of their accuracy with specimens from diverse settings across sub-Saharan Africa. We conducted a standardized, centralized evaluation of eight HIV RDTs and two simple confirmatory assays at a WHO collaborating centre for evaluation of HIV diagnostics using specimens from six sites in five sub-Saharan African countries. Methods: Specimens were transported to the Institute of Tropical Medicine (ITM), Antwerp, Belgium for testing. The tests were evaluated by comparing their results to a state-of-the-art reference algorithm to estimate sensitivity, specificity and predictive values. Results: 2785 samples collected from August 2011 to January 2015 were tested at ITM. All RDTs showed very high sensitivity, from 98.8% for First Response HIV Card Test 1–2.0 to 100% for Determine HIV 1/2, Genie Fast, SD Bioline HIV 1/2 3.0 and INSTI HIV-1/HIV-2 Antibody Test kit. Specificity ranged from 90.4% for First Response to 99.7% for HIV 1/2 STAT-PAK with wide variation based on the geographical origin of specimens. Multivariate analysis showed several factors were associated with false-positive results, including gender, provider-initiated testing and the geographical origin of specimens. For simple confirmatory assays, the total sensitivity and specificity was 100% and 98.8% for ImmunoComb II HIV 12 CombFirm (ImmunoComb) and 99.7% and 98.4% for Geenius HIV 1/2 with indeterminate rates of 8.9% and 9.4%. Conclusions: In this first systematic head-to-head evaluation of the most widely used RDTs, individual RDTs performed more poorly than in the WHO evaluations: only one test met the recommended thresholds for RDTs of ≥99% sensitivity and ≥98% specificity. By performing all tests in a centralized setting, we show that these differences in performance cannot be attributed to study procedure, end-user variation, storage conditions, or other methodological factors. These results highlight the existence of geographical and population differences in individual HIV RDT performance and underscore the challenges of designing locally validated algorithms that meet the latest WHO-recommended thresholds

Addfile 1 crude RDTs 04072016.pdf

Additional files to diagnostic accuracy study of HIV tests<br