Longitudinal Performance of Self-Reported ART Adherence Compared With Tenofovir Diphosphate in Dried Blood Spots in South Africa.

BACKGROUND

Self-reported ART adherence is widely used in resource-limited settings but may not accurately reflect cumulative drug exposure. Few longitudinal studies in sub-Saharan Africa have directly compared self-report with pharmacologic adherence measures, specifically tenofovir diphosphate concentrations (TFV-DP) in dried blood spots (DBS).

SETTING

Observational cohort study conducted in four public-sector ART clinics in Cape Town, South Africa.

METHODS

We analyzed data from 250 adults living with HIV, followed monthly for 13 visits. Participants reported missed ART doses in the prior 30 days and provided DBS for TFV-DP concentration. Longitudinal associations between missed doses and TFV-DP were examined using generalized estimating equations. Receiver operating characteristic (ROC) analyses evaluated the ability of SR to identify low TFV-DP in DBS (<699 fmol/punch). Logistic GEE models assessed the association between self-reported nonadherence and low TFV-DP.

RESULTS

Most participants were female (78%), median age 34 years (IQR, 27-42). Median TFV-DP concentrations declined with increasing self-reported missed doses: 1206 (IQR, 943-1442), 1009 (IQR, 773-1364), and 859 (IQR, 542-1194) fmol/punch for 0, 1-2, and ≥3 missed doses, respectively. Each additional missed dose was associated with lower TFV-DP concentrations in adjusted models (β = -29.2 fmol/punch per missed dose; p<0.001). Reporting ≥2 missed doses was associated with higher odds of low TFV-DP in longitudinal models (adjusted OR 1.50; p<0.001).

CONCLUSIONS

Self-report missed doses correlated with TFV-DP concentrations over time but lacked sensitivity for detecting low drug exposure. Self-report remains pragmatic but may be optimized when paired with objective biomarkers to identify those at risk for treatment failure.