Field performance of a thin-layer chromatography assay for detection of nevirapine in umbilical cord blood

• Published in: HIV clinical trials Vol. 7; no. 5; p. 263
• Main Authors: Chi, Benjamin H, Lee, Alison, Acosta, Edward P, Westerman, Larry E, Sinkala, Moses, Stringer, Jeffrey S A
• Format: Journal Article
• Language: English
• Published: England 01.09.2006
• Subjects: Algorithms; Anti-HIV Agents - pharmacokinetics; Anti-HIV Agents - therapeutic use; Chromatography, High Pressure Liquid; Chromatography, Thin Layer - economics; Cost-Benefit Analysis; Female; Fetal Blood - metabolism; HIV; HIV Infections - metabolism; HIV Infections - prevention & control; HIV Infections - transmission; Humans; Infant, Newborn; Infectious Disease Transmission, Vertical - prevention & control; Nevirapine - pharmacokinetics; Nevirapine - therapeutic use; Pregnancy; Pregnancy Complications, Infectious - metabolism; Pregnancy Complications, Infectious - prevention & control; Prospective Studies; Sensitivity and Specificity; Treatment Outcome; Zambia; Zambia
• ISSN: 1528-4336
• DOI: 10.1310/hct0705-263

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. 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. 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. 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.