Drug concentrations in hair and dried blood spots as PrEP adherence metrics during pregnancy and postpartum.

We evaluated hair tenofovir (TFV) concentrations as an adherence metric for HIV pre-exposure prophylaxis (PrEP) during pregnancy and postpartum and compared hair levels with tenofovir-diphosphate (TFV-DP) levels in dried blood spots (DBS). Overall, 152 hair samples from 102 women and 36 hair-DBS paired samples from 29 women were collected from a subset of women in a cluster randomized trial. Having a partner known to be living with HIV was associated with higher hair TFV levels (p<0.001). Hair TFV concentrations were strongly correlated with DBS TFV-DP levels (r=0.76, p<0.001), indicating hair as promising cumulative adherence metric for perinatal PrEP assessment.