Journal of clinical microbiology 2017 05 03() pii 10.1128/JCM.00176-17
Introduction: Although Roche COBAS Ampliprep/COBAS Taqman (CAP/CTM) systems are widely used in sub-Saharan Africa for early infant diagnosis of HIV from Dried blood spots (DBS), viral load monitoring with this system is not practical due to non-specific extraction of both cell free and cell associated viral nucleic acids. A simplified DBS extraction technique for cell free virus elution (FVE) using phosphate buffered saline (PBS) may provide an alternative analyte for lower cost quantitative HIV virus load (VL) testing to monitor antiretroviral therapy (ART).Methods: We evaluated the CAP/CTM V. 2.0 assay in 272 paired plasma and DBS specimens using the FVE method, and determined the level of agreement, sensitivity and specificity at thresholds of target not detected (TND) or below the limit of quantification (BLQ) (<20 copies/mL in plasma or <400 copies/mL in DBS), VL<1000 copies/mL and VL<5000 copies/mL.Results: Reported plasma VL ranged from TND, <20 to 5,781,592 copies/mL and DBS VL ranged from TND, <400 to 467,600 copies/mL. At <1000 copies/mL, agreement between DBS and plasma was 96.7% (kappa coefficient 0.93, p<0.0001). The mean difference between DBS and plasma VL values was -1.06 log10 copies/mL (95%CI -1.17, -0.97; p<0.0001). At a treatment failure threshold of >1000 copies/mL the sensitivities, specificities, PPV and NPV were 92.7%, 100%, 100% and 94.3% respectively.Conclusion: PBS elution of DBS offers a sensitive and specific method to monitor plasma viremia among adults and children on ART at the WHO recommended threshold of >1000 copies/ml on the Roche COBAS Ampliprep/COBAS Taqman (CAP/CTM) system.