Performance of patient-collected dried blood specimens for HIV-1 viral load testing in South Africa

Evaluate the clinical utility of patient-collected dried blood spots (DBS) in measuring HIV-1 viral load (VL) for monitoring antiretroviral therapy (ART) compared to provider-collected DBS and blood plasma.

In a randomized trial of community-based delivery of ART in South Africa, we assessed performance of: DBS specimens compared to plasma, and participant-collected vs. staff-collected DBS specimens, to measure HIV-1 VL.

The bioMérieux NucliSENS EasyQ HIV-1 v2.0 assay was used for VL measurement. From October 2017 to November 2019, we collected 996 pairs of plasma/DBS specimens from 760 participants and 315 pairs of staff-/participant-collected DBS cards from 261 participants. We assessed DBS test sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) using the WHO failure threshold of 1000 copies/ml. Log-transformed VL was compared using concordance correlation coefficients (CCC) and mean differences from linear mixed models.

In a population with 13% detectable VL, DBS VL compared with plasma VL had 91% [95% confidence interval (CI): 86-95] sensitivity, 99% (98-100) specificity, 94% (90-98) PPV, and 99% (98-99) NPV. We observed high agreement between staff-collected DBS VL and plasma VL (CCC: 0.94), and between participant-collected DBS VL and plasma VL (CCC: 0.92). We did not observe a statistically significant difference between participant- and staff-collected DBS VL and correlation was very high (CCC: 0.97).

VL results from participant-collected DBS are clinically comparable with those collected by clinical staff and using blood plasma. Self-collected DBS has potential for use for ART monitoring outside the clinic.