Viral load quantification:
Twelve studies evaluated DBS (approximately 1,100 specimens, not reported for one study), nine studies evaluated DPS (917 specimens) and no study evaluated DSS. The reported lower limits of detection for DBS at specimen a volume of 100μL ranged from 2.9 to 3.3 log10 RNA copies/mL (four studies). Correlation coefficients for DBS compared with liquid plasma specimens ranged from 0.72 to 0.99 (eight studies). Median differences between DBS and liquid plasma specimens were less than 0.5 log10 RNA copies/mL (five studies). Reported lower limits of detection for DPS at specimen a volume of 50 μL, ranged from 3 to 3.6 log10 RNA copies/mL (three studies); the lower limit of detection was 3 log10 RNA copies/mL at a specimen volume of 200 μL (one study). The correlation coefficients for DPS compared with liquid plasma specimens ranged form 0.86 to 0.97 (four studies). Median differences between DPS and liquid plasma specimens were <0.7 log10 RNA copies/mL (three studies). Five studies evaluated the correlation between DBS and DPS and significant correlation was found by four studies.
Resistance genotyping:
Nine studies evaluated DBS, two studies evaluated DPS and two studies evaluated DSS. For DBS specimens, amplification success rates ranged from 58% to 95% (eight studies); amplification success rates tended to be higher for higher viral loads (>3 log10 RNA copies/mL). Reported concordance between nucleic acid sequences generated from DBS and liquid plasma specimens was between 98.5% and 99.9% (five studies, six data sets) and reported concordance of drug resistance-associated codons detected from DBS and liquid plasma specimens was between 44% and 100% (seven studies, eight data sets). For DPS/DSS genotyping was considered reliable for viral load values above 4 log10 RNA copies/mL from 20 μL samples.
Nucleic acid stability:
Adequate nucleic acid stability was reported for a variety of sample storage conditions (full details were reported in the paper).