Simple amplification-based assay: a nucleic acid-based point-of-care platform for HIV-1 testing.

BACKGROUND: A new nucleic acid-based assay (simple amplification-based assay [SAMBA]) for rapid visual detection of human immunodeficiency virus-type 1 (HIV-1) by dipstick is described. The assay was designed to be simple, stable, robust, self-contained, and capable of detecting a broad spectrum of HIV-1 subtypes and recombinant forms. METHODS: The performance of the SAMBA HIV-1 test (amplification and detection chemistry) was evaluated using the World Health Organization HIV-1 RNA Genotype Reference Panel, with clinical samples representing various viral subtypes and recombinant forms common in sub-Saharan Africa. Sixty-nine randomly selected and blinded clinical samples that had undergone HIV-1 genotypic resistance analyses in a large London teaching hospital were also tested. These samples included 14 different viral subtypes or recombinant forms with viral loads of 78-9.5 x 10(6) copies/mL. RESULTS: The sensitivity and viral subtype coverage of the SAMBA HIV-1 test were either comparable to or better than those of the commercially available nucleic acid-based HIV-1 diagnostic tests. CONCLUSIONS: The unique characteristics and competitive performance of the SAMBA HIV-1 test render it suitable for point-of-care and near-patient testing in both developed and developing countries.

Optimal method of collection of first-void urine for diagnosis of Chlamydia trachomatis infection in men.

First-void urine (FVU) is the preferred specimen for the diagnosis of urogenital Chlamydia trachomatis infection in men. We have developed FirstBurst, a urine collection device that collects the first 4 to 5 ml of FVU and yields a specimen with a sixfold higher C. trachomatis organism load than the regular urine cup by quantitative PCR (32,533 versus 5,271 plasmids/ml; P < 0.0001). Consequently, the use of FirstBurst to collect a urine sample improved the sensitivity of a rapid test for Chlamydia over testing of samples collected with a urine cup (82 versus 47% sensitivity using PCR as a reference; P < 0.0015).

Field evaluation of a rapid point-of-care assay for targeting antibiotic treatment for trachoma control: a comparative study.

BACKGROUND: Trachoma results from repeated episodes of conjunctival infection with Chlamydia trachomatis and is the leading infectious cause of blindness. To eliminate trachoma, control programmes use the SAFE strategy (Surgery, Antibiotics, Face cleanliness, and Environmental improvement). The A component is designed to treat C trachomatis infection, and is initiated on the basis of the prevalence of the clinical sign trachomatous inflammation-follicular (TF). Unfortunately, TF correlates poorly with C trachomatis infection. We sought to assess a newly developed point-of-care (POC) assay compared with presence of TF for guiding the use of antibiotics for trachoma control. METHODS: We compared performance outcomes of the POC assay and presence of TF using commercial PCR as a comparator in 664 children aged 1-9 years in remote, trachoma-endemic villages in Tanzania. Signs of trachoma were graded according to the WHO simplified trachoma grading system. FINDINGS: Of 664 participants, 128 (19%) were positive for ocular C trachomatis infection by PCR. Presence of TF had a sensitivity of 64.1% (95% CI 55.8-72.4), specificity of 80.2% (76.8-83.6), and positive predictive value of 43.6% (36.5-50.7). By contrast, the POC assay had a sensitivity of 83.6% (77.2-90.0), specificity of 99.4% (98.8-100.0), and positive predictive value of 97.3% (94.2-100.3). Interagreements and intra-agreements between four novice operators were 0.988 (0.973-1.000) and 0.950 (0.894-1.000), respectively. INTERPRETATION: The POC assay is substantially more accurate than TF prevalence in identifying the presence or absence of infection. Additional studies should assess the use of the assay in the planning and monitoring of trachoma control activities.

Performance of the SAMBA I and II HIV-1 Semi-Q Tests for viral load monitoring at the point-of-care.

Although access to antiretroviral therapy for HIV infection is increasing in resource-poor countries, viral load testing for monitoring of treatment efficacy remains limited, expensive, and confined to centralized laboratories. The SAMBA HIV-1 Semi-Q Test is a nucleic acid-based amplification assay developed for viral load monitoring performed on either the semi-automated SAMBA I system for laboratory use or the fully automated SAMBA II system for point-of care use. We have assessed the performance characteristics of the SAMBA HIV-1 Semi-Q Test on SAMBA I and SAMBA II systems according to the Common Technical Specifications of the European Community's 98/79 In Vitro Diagnostic Medical Devices Directive. The sensitivity, specificity, reproducibility, and viral subtype coverage of the test were similar on the SAMBA I and SAMBA II platforms. The clinical performance on the SAMBA I system was compared with the Roche CAP/CTM assay and evaluated in-house with 130 patient specimens from London as well as in the field with 390 specimens in Kenya and Zimbabwe. The overall concordance between the SAMBA and CAP/CTM assays was 98.1%. The clinical performance of the test on the SAMBA II platform in comparison with the Abbott HIV-1 RealTime Assay was evaluated in-house with 150 specimens from Ukraine, yielding a concordance of 98.0%. The results thus show that the SAMBA HIV-1 Semi-Q Test performs equivalently on SAMBA I and SAMBA II, and they suggest that the test is suitable for implementation at the point-of-care in resource-poor regions where viral load testing is desperately needed but often unavailable.

Performance evaluation of the point-of-care SAMBA I and II HIV-1 Qual whole blood tests.

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.