PURPOSE: Although cord blood surveillance can measure the effectiveness of nevirapine (NVP)-based programs for the prevention of mother-to-child HIV transmission (PMTCT), it requires the ability to detect nevirapine in plasma. At present, the only validated method is high-performance liquid chromatography (HPLC), a technique poorly suited for most resource-constrained settings. METHOD: We evaluated the field performance for a simple and inexpensive thin-layer chromatography (TLC) assay for NVP detection. We developed a conditional probability model to compare 2 testing algorithms: HPLC alone, and TLC screening followed by HPLC confirmation of negative results. RESULTS: When compared to HPLC, sensitivity of TLC was 0.67 (95% confidence interval [CI] 0.49-0.84) and specificity was 0.84 (95% CI 0.69-0.95). In this sample - where overall NVP coverage was 49% - positive predictive value was 0.80 and negative predictive value was 0.72. At baseline with population NVP coverage of 33%, cost per specimen was lower in the TLC-HPLC testing algorithm (40 dollars vs. 50 dollars), and the proportion of false results was acceptable (11%). As population NVP coverage increased, cost-efficiency improved and error rate dropped substantially. CONCLUSION: TLC is reasonably sensitive and specific for NVP detection. A 2-step testing algorithm incorporating TLC and HPLC provides cost-efficiency at little expense to test performance.
PURPOSE: Although cord blood surveillance can measure the effectiveness of nevirapine (NVP)-based programs for the prevention of mother-to-child HIV transmission (PMTCT), it requires the ability to detect nevirapine in plasma. At present, the only validated method is high-performance liquid chromatography (HPLC), a technique poorly suited for most resource-constrained settings. METHOD: We evaluated the field performance for a simple and inexpensive thin-layer chromatography (TLC) assay for NVP detection. We developed a conditional probability model to compare 2 testing algorithms: HPLC alone, and TLC screening followed by HPLC confirmation of negative results. RESULTS: When compared to HPLC, sensitivity of TLC was 0.67 (95% confidence interval [CI] 0.49-0.84) and specificity was 0.84 (95% CI 0.69-0.95). In this sample - where overall NVP coverage was 49% - positive predictive value was 0.80 and negative predictive value was 0.72. At baseline with population NVP coverage of 33%, cost per specimen was lower in the TLC-HPLC testing algorithm (40 dollars vs. 50 dollars), and the proportion of false results was acceptable (11%). As population NVP coverage increased, cost-efficiency improved and error rate dropped substantially. CONCLUSION: TLC is reasonably sensitive and specific for NVP detection. A 2-step testing algorithm incorporating TLC and HPLC provides cost-efficiency at little expense to test performance.
Authors: Albert Y Liu; Qiyun Yang; Yong Huang; Peter Bacchetti; Peter L Anderson; Chengshi Jin; Kathy Goggin; Kristefer Stojanovski; Robert Grant; Susan P Buchbinder; Ruth M Greenblatt; Monica Gandhi Journal: PLoS One Date: 2014-01-08 Impact factor: 3.240