Objective: Dried blood spots (DBS) are a convenient alternative to plasma for drug resistance testing in resource-limited settings. We investigated the correlation between resistance genotypes generated from DBS and plasma.
Design: Sixty DBS specimens from HIV-1 subtype B-infected antiretroviral-experienced (n = 58) and naive patients (n = 2) were tested. DBS were prepared using 50 mul blood and were stored with desiccant at -20 degrees C.
Methods: Resistance genotypes from DBS were obtained using the ViroSeq HIV-1 assay and were compared with genotypes derived from plasma. The frequency of amplification of proviral DNA from DBS was evaluated using an in-house nested polymerase chain reaction assay.
Results: : Fifty of the 60 DBS specimens were successfully genotyped including all 38 specimens collected from patients with plasma viral loads greater than 2000 copies/ml and 12 of 22 DBS (54.5%) from patients with viral loads less than 2000 copies/ml. HIV-1 DNA was detected in 44.4% of the DBS. Despite the presence of DNA, genotypes from DBS and plasma were highly concordant. Of the 316 mutations found in plasma sequences, 306 (96.8%) were also found in DBS. Discrepancies were mostly caused by mixtures at minor protease positions or unusual amino acid changes, and in only two cases were caused by major protease (M46L) or reverse transcriptase (K103N) mutations absent in DBS sequences.
Conclusion: : We demonstrated a high concordance between resistance genotypes from plasma and DBS, and that resistance testing from DBS can achieve sensitive levels similar to those seen using plasma. Our results indicate that DBS may represent a feasible alternative to plasma for drug resistance testing in treated individuals.