This observational study found that half of the patient with negative IgM and RT-qPCR-positive SARS-CoV-2 had severe COVID-19 disease.
- IgM-based gold immunochromatographic assay (GICA) is the test used within this study, to investigate its utility
- Severe cases were defined as patients requiring ICU level care and receiving treatment for 3 days.
- The IgM-GICA positivity from the RT-qPCR confirmed COVID-19 patients is shown to be 82.2% (37/45)
- Specificity testing of IgM-GICA did not detect SARS-CoV-2 antibodies in human sera infected with other viruses or from healthy people
- IgM detection rates were substantially lower in patients who progressed to severe disease as opposed to mild disease:
- At 4–7 days after symptom onset, the positive rate of the mild group was 64% (16/25), compared to 16.7% (1/6) in the severe group
- At 15–21 days after symptom onset, the positive rate of the mild group was 100% (15/15), compared to 75% (6/8) in the severe group
