Waning antibody levels correspondence in NEJM (Free) ：IgG抗体の半減期が70日程度とのこと．こんな短い期間で半減してしまうのであれば，疫学調査にはとてもじゃないが，使えない．
Waning antibody levels after mild illness: Thirty-four volunteers who had recovered from COVID-19 illness -- mostly mild -- had their IgG antibody levels assessed at a mean of 37 and 86 days after symptom onset. The observed reduction in IgG levels corresponded to a half-life of roughly 73 days. The authors write in the New England Journal of Medicine: "Our findings raise concern that humoral immunity against SARS-CoV-2 may not be long lasting in persons with mild illness, who compose the majority of persons with Covid-19."
PHYSICIAN'S FIRST WATCH for July 1, 2020
検査会社への外注ではなく）臨床現場（point-of-care）での使用可能なLFIA法（Lateral flow immunoassays ）の感度は66％と，検査会社の中央ラボで使われているCLIA（94%）やELISA（84%）に比べて感度が非常に低く，使い物にならない．
Antibody test accuracy: Lateral flow immunoassays (LFIAs) -- antibody assays potentially used as point-of-care tests -- have the lowest sensitivity of SARS-CoV-2 antibody tests studied, according to a meta-analysis in The BMJ. Researchers examined 40 studies that evaluated the accuracy of antibody tests with RT-PCR as the reference standard (half the studies were not peer-reviewed). Overall, the sensitivity of chemiluminescent immunoassays (CLIAs) for IgG or IgM was roughly 98%; enzyme-linked immunosorbent assays (ELISAs), 84%; and LFIAs, 66%. Test sensitivity was highest 3 or more weeks after symptom onset. The researchers note that the data were "characterised by high risks of bias, heterogeneity, and limited generalisability to point-of-care testing and to outpatient populations." They add that "the available evidence does not support the
continued use of existing point-of-care serological tests."
Diagnostic accuracy of serological tests for covid-19: systematic review and meta-analysis
COVID-19: Antibody Test Accuracy
Antibody test accuracy: Tests for IgG/IgM antibodies against SARS-CoV-2 have a sensitivity of just 30% during the first week of symptoms, rising to 91% during the third week, according to a review of 38 studies published by Cochrane Library. Data beyond 3 weeks were limited. Overall, test specificity was above 98%. The researchers say that while antibody tests "may still have a role complementing other testing in individuals presenting later, when RT PCR tests are negative, or are not done," the limited data beyond 3 weeks calls into question "the utility of these tests for seroprevalence surveys for public health management purposes." Of note, the evaluated tests included both
point-of-care and laboratory-based tests.
Cochrane review of antibody test findings (Free)