Use of Hair Samples for Monitoring of Antiretroviral Therapy Adherence

Introduction: Measurement of antiretrovirals (ARVs) drug concentration in biological matrices such as blood and urine has been used previously for monitoring adherence. Unfortunately, they only reflect ARV doses taken within 1 to 2 days of sampling. Hair testing has become the most preferred tool to determine chronic exposure to some drugs, especially drugs of abuse, because of its long detection window. Objective: This study, evaluated the utility of hair samples in therapeutic drug monitoring (TDM) as an indicator of ART adherence. Methods: This study used nevirapine (NVP), an ARV integral component of the first line ART in Kenya, for many years. Matched hair and blood samples were obtained from 234 and 328 consenting HIV patients on first line ART with virologic failure (viral load >1000 copies/mL) and suppressed viral load (VL<1000 copies/mL) respectively. The ARV plasma and hair concentrations were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results: The calculated median; interquartile range (IQR) of NVP levels in hair and plasma samples were 36.8ng/ mL and 19.32ng/mL respectively. There was no significant difference between the level of NVP in hair and matched plasma samples (Wilcoxon signed rank test; Z = -0.93, P> 0.05). Conclusion: The study has demonstrated that analysis of ARV drugs in the hair can determine drug exposure as an alternative to conventional plasma drug analysis, especially in our settings where laboratory facilities and skilled personnel to do phlebotomy are few or lacking.