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. 2021 Jan;13(1):13-28.
doi: 10.4155/bio-2020-0289. Epub 2020 Dec 15.

Validation of dried blood spot sample modifications to two commercially available COVID-19 IgG antibody immunoassays

Theodore T Zava  1 , David T Zava  1
Affiliations

Validation of dried blood spot sample modifications to two commercially available COVID-19 IgG antibody immunoassays

Theodore T Zava et al. Bioanalysis. 2021 Jan.

Abstract

Aim: Coronavirus disease 2019 antibody testing often relies on venous blood collection, which is labor-intensive, inconvenient and expensive compared with finger-stick capillary dried blood spot (DBS) collection. The purpose of our work was to determine if two commercially available anti-severe acute respiratory syndrome coronavirus 2 enzyme-linked immunosorbent assays for IgG antibodies against spike S1 subunit and nucleocapsid proteins could be validated for use with DBS. Materials & methods: Kit supplied reagents were used to extract DBS, and in-house DBS calibrators were included on every run. Results: Positive/negative concordance between DBS and serum was 100/99.3% for the spike S1 subunit assay and 100/98% for the nucleocapsid assay. Conclusion: Validation of the DBS Coronavirus disease 2019 IgG antibody assays demonstrated that serum and DBS can produce equivalent results with minimal kit modifications.

Keywords: COVID-19; DBS; ELISA; IgG; SARS-CoV-2; antibody; dried blood spot; filter paper; pandemic.

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Figures

Figure 1.
Figure 1.. Interassay precision and month long stability.
Interassay precision and month-long stability of seven study subject DBSs stored at -80°C to 55°C over 30 days run on the (A) ZRT DBS IgG S1 and (B) ZRT DBS IgG NCP assays. DBS: Dried blood spot.
Figure 2.
Figure 2.. Extracted dried blood spots in the fritted filter block at day 14 of interassay precision/stability testing with marked samples representing DBS from seven study subjects stored at 55°C showing partial extraction.
DBS: Dried blood spot.
Figure 3.
Figure 3.. Serum versus dried blood spot raw absorbance comparison.
Raw assay absorbance comparison between the (A) ZRT DBS IgG S1 and the EUROIMMUN serum IgG antibody assays and the (B) ZRT DBS IgG NCP and Epitope Diagnostics serum IgG antibody assays (n = 177). DBS: Dried blood spot.
Figure 4.
Figure 4.. Negative/indeterminate/positive antibody detection cutoffs.
Absorbance from all study subject DBSs run on the (A) ZRT DBS IgG S1 and (B) ZRT DBS IgG NCP assays, organized from the lowest to highest, to visually determine seropositivity cutoffs of negative, indeterminate and positive. Seropositivity cutoffs were verified using PCR-confirmed results on the (C) ZRT DBS IgG S1 and (D) ZRT DBS IgG NCP assays (n = 43). DBS: Dried blood spot; PCR: Polymerase chain reaction.
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