Diagnostic value and dynamic variance of serum antibody in coronavirus disease 2019

Yujiao Jin, Miaochan Wang, Zhongbao Zuo, Chaoming Fan, Fei Ye, Zhaobin Cai, Ying Wang, Huaizhong Cui, Kenu Pan, Aifang Xu. Diagnostic value and dynamic variance of serum antibody in coronavirus disease.
International Journal of Infectious Diseases, May 2020. Volume 94, Pages 49-52, ISSN 1201-9712. https://doi.org/10.1016/j.ijid.2020.03.065.

Review written by:

Qian Ma, edited by Gizem Efe

Yellow - Moderate evidence, limited by small sample size, retrospective study, difference in demographics/clinical characteristics of groups, variance in intervals between different testing modalities

  • Retrospective study done in Hangzhou, China. 43 patients were enrolled in the experimental group vs. 33 patients in the control group.

  • Both experimental and control groups had similar symptoms (fever and cough predominated) but were distinguished by results of COVID-19 PCR testing. Overall, the experimental group included a greater proportion of women and older subjects than the control group.

  • Compared to RT-PCR detection as gold standard, the sensitivity of serum IgM and IgG antibodies to diagnose COVID-19 were 48.1% and 88.9% respectively, and the specificity were 100% and 90.9% respectively.

  • The positive predictive values of IgM and IgG antibodies were 100% and 88.9% respectively, and the negative predictive values were 70.2% and 90.9%.

  • Serological titers are negative/low in the first 5 days after symptom onset of COVID-19 patients (n=6 patients).

  • Both IgM and IgG remained positive after negative conversion of RT-PCR testing. Of note, IgG titer doubled (p<0.001) after viral testing became negative. Whether this correlates with better clinical outcome or future resistance is unknown.

Review Notes
  1. Small sample size, retrospective study. Apparent differences exist between experimental and control groups, including age, sex, and hypertension history.

  2. The interval between RT-PCR detection and serological testing varies and was not normalized.

  3. The interval between symptom onset and serological testing is long (median duration is about 20 days) because the serology kit was available late, therefore relatively few patients were tested using serological method during the early stage of disease.

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