Minority HIV mutation detection in dried blood spots indicates high specimen integrity and reveals hidden archived drug resistance

BackgroundDried blood spots (DBS) could serve as an attractive, cost-effective alternative to plasma for HIV drug resistance testing.ObjectivesTo assess the utility and potential gain in genotypic information with sensitive testing of DBS compared to conventional bulk plasma genotyping, and examine the correlation of majority and minority-level resistance mutations in DBS with treatment history.Study designEvaluate nucleic acids from the DBS of 33 antiretroviral-experienced subtype B-infected subjects for minority M41L, K65R, K70R, K103N, Y181C, M184V, and T215Y/F mutations by real-time PCR. Compare minority resistance mutations in DBS with bulk genotypes from the same DBS cards and available plasma specimens.ResultsAll but one (50/51, 98%) mutation from the original plasma bulk sequencing were still detectable in the DBS after three years of storage. The one mutation not identified in DBS was also no longer detectable by bulk sequencing. Furthermore, sensitive testing found 12 additional drug resistance mutations at minority levels in the DBS of 11 (33%) patients. Six minority mutations were in the RNA compartment and six were detected only in the DNA compartment. Resistance was detected in the DBS RNA compartment only in cases where the associated drug was in use within one year of sample collection.ConclusionsOur ability to identify majority and additional minority-level resistance mutations demonstrated that DBS, if stored properly, is a high-integrity specimen type for conventional and sensitive drug resistance testing. Our data further support the global utility of DBS for drug resistance surveillance and clinical monitoring.