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Designing HIV Testing Algorithms Based on 2015 WHO Guidelines Using Data from Six Sites in sub-Saharan Africa(American Society for Microbiology, 2017-07-26)Our objective was to evaluate the performance of HIV testing algorithms based on WHO recommendations, using data from specimens collected at six HIV testing and counselling sites in sub-Saharan Africa (Guinea, Conakry; Kitgum and Arua, Uganda; Homa Bay, Kenya; Douala, Cameroun; Baraka, Democratic Republic of Congo). A total of 2780 samples, including 1306 HIV-positive, were included in the analysis. HIV testing algorithms were designed using Determine as a first test. Second and third rapid diagnostic tests (RDT) were selected based on site-specific performance, adhering where possible to the WHO-recommended minimum requirements of sensitivity and specificity of ≥99%. The threshold for specificity was reduced to 98% or 96% if necessary. We also simulated algorithms consisting of one RDT followed by a simple confirmatory assay. The positive predictive values (PPV) of the simulated algorithms varied from 75.8%-100% using strategies recommended for high-prevalence settings; 98.7%-100% using strategies recommended for low-prevalence settings; and 98.1%-100% using a rapid test followed by a simple confirmatory assay. Although we were able to design algorithms that met the recommended PPV of ≥99% in five of six sites using the applicable high prevalence strategy, options were often very limited due to sub-optimal performance of individual RDTs and to shared false-reactive results. These results underscore the impact of the sequence of HIV tests and of shared false-reactivity on algorithm performance. Where it is not possible to identify tests that meet WHO-recommended specifications, the low-prevalence strategy may be more suitable.
Prospective Evaluation of the Diagnostic Accuracy of Dried Blood Spots from Finger-Prick for the Determination of HIV-1 Viral Load with the NucliSENS Easy-Q HIV-1 v2.0 in Malawi(American Society for Microbiology, 2014-02-05)HIV-1 viral load (VL) testing is not widely available in resource-limited settings. Use of finger-prick dried blood spot (FP-DBS) samples could remove barriers related to sample collection and transport. Measurement of VL using DBS from EDTA venous blood (VB-DBS) in place of plasma has previously been validated using the NucliSENS EasyQ HIV-1 v2.0 assay, but information on the accuracy of FP-DBS samples for measuring VL is limited. This prospective study, conducted at Thyolo District Hospital in Southern Malawi, compared VL levels measured on FP-DBS samples and plasma, using the NucliSENS EasyQ HIV-1 v2.0 assay. Comparability was assessed by means of agreement and correlation (131 patients with VLs ≥100 copies/ml), and sensitivity and specificity (612 patients on ART). Samples of EDTA venous blood and FP-DBS from 1,009 HIV-infected individuals were collected and prepared in the laboratory. Bland-Altman analysis found good agreement between plasma and FP-DBS VL levels, with a mean difference of -0.35 log10, and 95% limits of agreement from -1.26 to 0.55 log10. FP-DBS had a sensitivity of 88.7% (95% confidence interval [CI]: 81.1 - 94.4%) and specificity of 97.8% (95% CI: 96.1 - 98.9%) using a 1,000 copies/ml cut-point; and a sensitivity of 83.0% (95% CI: 73.4 - 90.1%) and specificity of 100% (95% CI: 99.3-100%) using a 5,000 copies/ml cut-point. This study shows that FP-DBS is an acceptable alternative to plasma for measuring VL using the NucliSENS EasyQ HIV-1 v2.0. We are conducting a second study to assess the proficiency of health workers at preparing FP-DBS in primary healthcare clinics.