Evaluation of Dried Blood Spots for Human Immunodeficiency Virus Type 1 Drug Resistance Testing

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Abstract
Dried blood spots (DBS) are simpler to prepare, store, and transport than plasma or serum and may represent a good alternative for drug resistance genotyping, particularly in resource-limited settings. However, the utility of DBS for drug resistance testing is unknown. We investigated the efficiency of amplification of large human immunodeficiency virus type 1 (HIV-1)polfragments (1,023 bp) from DBS stored at different temperatures, the type of amplified product(s) (RNA and/or DNA), and the similarity between plasma and DBS sequences. We evaluated two matched plasma/DBS panels stored for 5 to 6 years at several temperatures and 40 plasma/DBS specimens collected from untreated persons in Cameroon and stored for 2 to 3 years at −20°C. The amplification of HIV-1polwas done using an in-house reverse transcriptase-nested PCR assay. Reactions were done with and without reverse transcription to evaluate the contribution of HIV DNA topolsequences from DBS. Amplification was successful for the DBS samples stored for 5 to 6 years at −20°C or at −70°C but not for those stored at room temperature. Thirty-seven of the 40 (92.5%) DBS from Cameroon were amplifiable, including 8/11 (72.7%) with plasma virus loads of 10,000. Proviral DNA contributed significantly to DBS sequences in 24 of the 37 (65%) specimens from Cameroon. The overall similarity between plasma and DBS sequences was 98.1%. Our results demonstrate the feasibility of DBS for drug resistance testing and indicate that −20°C is a suitable temperature for long-term storage of DBS. The amplification of proviral DNA from DBS highlights the need for a wider evaluation of the concordance of resistance genotypes between plasma and DBS.

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