Prospective Evaluation of the Diagnostic Accuracy of Dried Blood Spots from Finger-Prick for the Determination of HIV-1 Viral Load with the NucliSENS Easy-Q HIV-1 v2.0 in Malawi

Abstract

HIV-1 viral load (VL) testing is not widely available in resource-limited settings. Use of finger-prick dried blood spot (FP-DBS) samples could remove barriers related to sample collection and transport. Measurement of VL using DBS from EDTA venous blood (VB-DBS) in place of plasma has previously been validated using the NucliSENS EasyQ HIV-1 v2.0 assay, but information on the accuracy of FP-DBS samples for measuring VL is limited. This prospective study, conducted at Thyolo District Hospital in Southern Malawi, compared VL levels measured on FP-DBS samples and plasma, using the NucliSENS EasyQ HIV-1 v2.0 assay. Comparability was assessed by means of agreement and correlation (131 patients with VLs ≥100 copies/ml), and sensitivity and specificity (612 patients on ART). Samples of EDTA venous blood and FP-DBS from 1,009 HIV-infected individuals were collected and prepared in the laboratory. Bland-Altman analysis found good agreement between plasma and FP-DBS VL levels, with a mean difference of -0.35 log10, and 95% limits of agreement from -1.26 to 0.55 log10. FP-DBS had a sensitivity of 88.7% (95% confidence interval [CI]: 81.1 - 94.4%) and specificity of 97.8% (95% CI: 96.1 - 98.9%) using a 1,000 copies/ml cut-point; and a sensitivity of 83.0% (95% CI: 73.4 - 90.1%) and specificity of 100% (95% CI: 99.3-100%) using a 5,000 copies/ml cut-point. This study shows that FP-DBS is an acceptable alternative to plasma for measuring VL using the NucliSENS EasyQ HIV-1 v2.0. We are conducting a second study to assess the proficiency of health workers at preparing FP-DBS in primary healthcare clinics.