Of the 30 specimens from infected patients, the in-house ELISA assay was positive for IgM and IgG in 22 (73.3%) and 26 (86.7%) patients, respectively. The BioMedomics antibody assay found 73.3% and 80% positivity for IgM and IgG, respectively, whereas the Premier Biotech assay found 70% and 73.3% positivity for IgM and IgG, respectively. The Abbott chemiluminescence microparticle assay was positive in 24 patients who were RT-PCR–positive and negative in all patients who were RT-PCR–negative. The 4 serological assays showed a specificity ranging from 96.7% to 100% for IgM and from 93.3% to 100% for IgG. The control line formed in each of the BioMedomics and Premier Biotech tests, indicating that the assays were properly functioning (Figure 1). See Table 3 for the sensitivity and specificity of all antibody assays included in our study.
Premier Diagnostics (top row) and BioMedomics (bottom row) lateral flow assays. Cartridges 13–15 illustrate positive results for both IgG and IgM, whereas cartridge 16 illustrates negative results for both IgG and IgM.
Our results also showed an increased sensitivity and specificity of the BioMedomics and Premier Biotech assays over time. The sensitivity and specificity of both assays for IgM and/or IgG in specimens collected >14 days after RT-PCR testing was 100%. See Table 4 for the sensitivity and specificity of the BioMedomics and Premier Biotech assays for IgM and/or IgG in specimens collected at different time intervals from the RT-PCR testing date.
Lab Med. 2022;53(3):262-265. © 2022 American Society for Clinical Pathology