Objectives: We evaluated an In-house assay for HIV-1 drug resistance genotyping by using DBS samples in China.
Methods: The amplification sensitivity was assessed using 79 DBS specimens with plasma viral load ranging from 1,000 to 6,000 copies/ml. Precision was assessed using 5 DBS specimens with 5 replicates tested in one test run. Reproducibility was evaluated using other 5 DBS specimens with 5 replicates genotyped in 5 test runs. Nucleotide sequence identity and the degree of concordance in detecting drug resistance mutations were assessed within and between test runs. In addition, nucleotide sequence and drug resistance mutations were compared between 64 matched plasma and DBS specimens.
Results: The amplification rate of DBS specimens with plasma viral load of 1,000-6,000 copies/ml was 96.2% (76/79). The nucleotide sequence identity was 99.7±0.34% and 99.6±0.25% within and between test runs, respectively. Moreover, there was a near perfect agreement of detecting drug resistance mutations intra- and inter- test runs with kappa value of 0.972 and 0.963, respectively. Between 64 pairs of plasma and DBS specimens, the nucleotide identity was excellent with 99.5±0.34%. As compared to the results of plasma specimens, the sensitivity and specificity for detecting drug resistance mutations in DBS specimens were 99.4 % (95% CI, 97.4-99.8%) and 99.8% (95% CI, 99.7-99.9%), respectively. Totally 15 discordant drug resistance mutations were found. Among them, 53.3 % (8/15) were caused by mixture base.
Conclusion: The In-house HIVDR genotyping assay could be used for testing DBS samples with viral load above 1,000 copies/ml in China and had a low intra- and inter- assay variability. DBS is an excellent alternative to plasma for HIV-1 drug resistance genotyping at population levels in China.