HemaSpotTM

HemaspotTM is a product series designed explicitly for dried blood specimen collection offered by Spot on Sciences (San Francisco, CA, USA), founded in 2010 (https://www. spotonsciences.com/, accessed on 20 March 2022). The HemaSpot HF device has been tested in HIVDR assays. The HemaSpot HF device is a moisture-tight cartridge containing a circular chamber. A spoked absorbent filter paper pad, a descant ring, and an application disk are layered from the bottom up. Once the fluid drops are loaded, the cartridge can be closed immediately. The built-in desiccant dries the sample in minutes, and the sample is then ready for shipment. Samples collected with HemaSpot devices closely mimic the DFPAs while easing the requirement for additional drying procedures and holding up to 200 μL of original liquid specimens. The moisture-tight design and the tamperresistant latch on the cartridge also help minimize the ambience's impact and retain the stability of the dried analyte it holds. Upon analysis, each spoke on the dried fluid pad can be plucked individually for multiple assays without punching, minimizing the risk of cross-contamination.

Dried blood analytes collected with HemaSpot have been applied as an alternative to DBS for serologic tests for several human viral pathogens [53–56]. While HemaSpot appears to be a promising technology, data on the usage of HemaSpot specimens for HIV molecular assays are scarce. Hirshfield et al. first confirmed the feasibility of using selfcollected HemaSpot blood specimens for HIV VL monitoring [57]. Brooks et al. pioneered applying dried whole blood prepared with HemaSpot devices in HIVDRT in 2016 [58]. They evaluated the performance of HemaSpot specimens prepared from either fresh blood at various VL dilutions and a storage time up to 4 weeks at room temperature, or thawed frozen whole blood, both at 100 μL. For all specimens at VL >1000 copies /mL, HIV typing was successful in 79% and 58% of HemaSpot specimens prepared from fresh and frozenthaw blood, respectively. The genotyping success rates improved significantly with a shorter storage period and higher VLs. The HIV PR and RT gene sequences derived from HemaSpot specimens show >96% identity compared to those from matching plasmas. In

addition, the HIVDR profiling concordance between the paired HemaSpot specimens and plasma was determined as 86% [58]. Considering the intrinsic differences between plasma and DBS analytes described above, such discrepancies are expectable. Nonetheless, this study showed that the HemaSpot is a promising dried blood sample collection technology that may promote expanded HIVDRT in RLS.

With the scarcity of follow-up studies on this technology, the findings from this pilot study remain to be confirmed by more comprehensive evaluations regarding its sensitivity, accuracy, and consistency. These may include verifying the findings from Brooks' study on dried whole blood and assessing the performance of dried plasma or serum specimens collected with the HemaSpot device in HIV molecular assays. Notably, the HemaSpot SE product is designed to separate and dry the cellular components and serum onto the same absorbent membrane, which may serve different analysis needs targeting serum/plasma or cellular components of blood with one analyte. Comprehensive studies on the suitability of specimens from HemaSpot SE device for HIV molecular assays remain to be conducted.
