DBS

DBS is the foremost DFPA option for HIVDRT. DBS is prepared by spotting and drying whole blood onto absorbent filter paper cards [40,41]. The blood could be from phlebotomy or a simple lancet-prick that even patients themselves can do. The small sample volume it requires (50~75 μL per spot) and no stringent need for phlebotomy make DBS an attractive option peculiarly for pediatric patients. The technical, practical, and operational advantages of DBS are evident. DBS can be naturally dried, packed, shipped in a regular envelope and stored at ambient temperature using zip-lock plastic bags with desiccant for days to weeks before processing. It helps avoid the requirement for cold-chain transportation while posing minimal biohazard peril to the ambience.

The performance of DBS in HIVDRT has been well-documented in varied contexts, and DBS is proven to be an accountable analyte for HIVDRT in most cases. Well-established DBS-based HIVDRT guidelines have been implemented [16]. With the proven success of DBS usage in HIVDRT from many studies, DBS is currently the WHO-recommended blood sampling method in low- to middle-income countries [16,42,43].

Although DBS is considered a suitable alternate analyte for HIVDRT, DBS has its intrinsic limitations. Like WB, the presence of proviral DNA in DBS renders a higher success rate for HIV amplification than DPS or DSS. However, such proviral DNA contribution also limits its capacity to manifest the HIVDR status of circulating replication-active HIV viruses. Studies have shown that proviral DNA in the DBS may contribute to up to 80% of the application success rates of these samples [44,45]. Steegen et al. successfully genotyped HIV PR and RT genes from 54.8% and 58.1% DBS DNA preparations from patients with undetectable plasma VL [18]. The comparability of DNased-treated extracts from DBS and DPS in HIV PCR success rates further confirms the proviral DNA contribution to the DBS-based HIV genotyping [45]. HIVDR profiling data from DBS and matching plasma are concordant only when the VL is ≥5000 copies/mL, and/or the patients have no ART experience, and/or the duration of HIV infection is short [27]. This restricts the DBS application in clinical HIVDR monitoring, for which low VL specimens from ART-treated patients are unavoidable.

DBS has been applied primarily in HIVDR surveillance and research studies. Occasionally, DBS was assessed for centralized HIVDR monitoring in which DBS specimens were collected from RLS where clinical monitoring is required, but DBS is the only feasible sampling option. Regardless of the success rate of HIVDRT in such studies, DBS is not an ideal option for HIVDR monitoring purposes. However, one exception is for HIV-infected pediatric patients, from whom collecting large blood volume via venipuncture is often impractical and unrealistic. With nearly half of the HIV-infected infants/children carrying HIVDR variants even before ART initiation in Sub-Saharan Africa, where HIV/AIDS hits the hardest, the advantage of DBS could be of particular significance in this patient category [3].
