Routine viral-load (VL) testing of HIV-infected individuals on antiretroviral therapy (ART) is used to monitor treatment efficacy. However, due to logistical challenges, implementation of VL has been difficult in resource-limited settings. The aim of this study was to evaluate the performance of the SAMBA semi-Q (simple amplification-based assay semiquantitative test for HIV-1) in London, Malawi, and Uganda. The SAMBA semi-Q can distinguish between patients with VLs above and below 1,000 copies/ml. The SAMBA semi-Q was validated with diluted clinical samples and blinded plasma samples collected from HIV-1-positive individuals. SAMBA semi-Q results were compared with results from the Roche COBAS AmpliPrep/COBAS TaqMan HIV-1 test, v2.0. Testing of 96 2- to 10-fold dilutions of four samples containing HIV-1 subtype C as well as 488 samples from patients in the United Kingdom, Malawi, and Uganda yielded an overall accuracy for the SAMBA semi-Q of 99% (95% confidence interval [CI], 93.8 to 99.9%) and 96.9% (95% CI 94.9 to 98.3%), respectively, compared to to the Roche test. Analysis of VL data from patients in Malawi and Uganda showed that the SAMBA cutoff of 1,000 copies/ml appropriately distinguished treated from untreated individuals. Furthermore, analysis of the viral loads of 232 patients on ART in Malawi and Uganda revealed similar patterns for virological control, defined as either <1,000 copies/ml (SAMBA cutoff) or <5,000 copies/ml (WHO 2010 criterion; WHO, Antiretroviral Therapy for HIV Infection in Adults and Adolescents: Recommendations for a Public Health Approach, 2010). This study suggests that the SAMBA semi-Q has adequate concurrency with the gold standard measurements for viral load. This test can allow VL monitoring of patients on ART at the point of care in resource-limited settings.

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The SAMBA HIV-1 Qual Whole Blood Test is a nucleic acid-based amplification assay for the qualitative detection of HIV-1 in whole blood of adults or infants. The test can be run on either the semi-automated SAMBA I system for clinical use or the fully automated, including readout, SAMBA II system for point-of-care use in resource-limited settings. We have assessed the performance characteristics of the SAMBA HIV-1 Qual Whole Blood Test on SAMBA I and SAMBA II. The limit of detection obtained for the two tests were 518IU/ml and 399copies/ml on SAMBA I and 457IU/ml and 433copies/ml on SAMBA II. Test specificity on both systems was 100% with a panel of 503 HIV-1 negative samples. Evaluation of test reproducibility showed 100% concordance with expected gold standard results as well as 100% agreement between operators, days, and runs as well as within runs on both SAMBA I and SAMBA II. Our results thus show that the SAMBA HIV-1 Qual Whole Blood Test performs equivalently on SAMBA I and SAMBA II, and also suggest that the test is suitable for implementation in medium-throughput clinical facilities (SAMBA I) or low-throughput point-of-care (POC) settings (SAMBA II) in resource-poor regions.