COVID-19 Evidence Alerts
from McMaster PLUSTM

Current best evidence for clinical care (more info)

Diagnosis Guo CC, Mi JQ, Nie H Seropositivity rate and diagnostic accuracy of serological tests in 2019-nCoV cases: a pooled analysis of individual studies. Eur Rev Med Pharmacol Sci. 2020 Oct;24(19):10208-10218. doi: 10.26355/eurrev_202010_23243.

OBJECTIVE: Currently, detection of SARS-CoV-2 RNA is standard in the diagnosis of COVID-19 (2019-nCoV). However, reliable and rapid serological diagnostic methods to screen SARS-CoV-2 infected patients, including those who do not have overt symptoms, are urgently needed. Most studies have described serological tests based on the detection of SARS-CoV-2-specific IgM and IgG. Here, we attempted to systematically analyze the positive rates and comprehensive diagnostic efficacy of IgM and IgG in response to SARS-CoV-2 infection.

MATERIALS AND METHODS: By systematically searching PubMed, medRxiv, bioRxiv and other databases, studies regarding the detection of peripheral blood IgM and/or IgG related to SARS-CoV-2 were collected. The positive rate, sensitivity (SEN), specificity (SPE), area under the curve (AUC) and corresponding 95% CIs were obtained by weighted quantitative mergence, and the source of heterogeneity was explored by performing a subgroup study and sensitivity analysis.

RESULTS: A total of 30 studies were included, which were comprised of 3856 confirmed SARS-CoV-2 RNA positive cases, 368 suspected RNA negative cases, 1167 asymptomatic carriers, and 2526 RNA negative controls. The corresponding meta-analysis showed that in confirmed cases with 2019-nCoV, the positive rates of single IgM, single IgG and their joint detection related to SARS-CoV-2 were 61.2% (95% CI: 53.4%-69.0%), 58.8% (95% CI: 49.6%-68.0%) and 62.1% (52.7%-71.4%), respectively. In suspected RNA negative cases, the positive rates of single IgM, single IgG and their joint detection were 29.0% (95% CI: 14.0%-44.0%), 37.0% (95% CI: 20.0%-55.0%) and 55.0% (95% CI: 19.0%-90.0%), respectively. Interestingly, IgM/IgG detection also demonstrated a positive rate of 19% (95% CI: 10.0%-27.0%) in asymptomatic cases. Using RT-PCR test as reference, the AUCs of IgM, IgG and IgM/IgG in the diagnosis of 2019-nCoV infection were 0.9656, 0.9766, and 0.9838, respectively. The stratified analyses showed that among confirmed cases with 2019-nCoV, the positive rates of IgM and IgG were 27.3% (95%CI: 19.8%-34.8%) and 22.3% (95% CI: 11.3%-33.3%), respectively, 0-7days following the onset of symptoms, whereas the positive rate of parallel IgM/IgG testing attained 39.3% (95% CI: 24.2%-54.4%). Moreover, the efficacy of antibody testing based on CLIA (chemiluminescence enzyme immunoassays) in diagnosing 2019-nCoV infection was higher than that of LFIA (lateral flow immunoassays) and ELISA (enzyme linked immunosorbent assay).

CONCLUSIONS: IgM, IgG and their joint testing exhibited high clinical value in the diagnosis of 2019-nCoV, which may assist in making up for the deficiency of throat swab RNA tests.

Discipline / Specialty Area Score
General Internal Medicine-Primary Care(US)
Family Medicine (FM)/General Practice (GP)
Public Health
Emergency Medicine
Hospital Doctor/Hospitalists
Internal Medicine
Infectious Disease
Comments from MORE raters

Family Medicine (FM)/General Practice (GP) rater

At the primary care level, we are limited as far as testing modalities by what the labs and public health have set up.

Hospital Doctor/Hospitalists rater

The most useful part of this analysis is the specificity of the Ab tests, confirming a very low likelihood of false-positives. Sensitivity is poor, however, and not adequate for diagnostic testing independent of PCR.

Infectious Disease rater

Not sure how helpful this is since it averages data from multiple studies and doesn’t help choose. Also, many of the included studies lacked data on timing of exposure or symptoms.

Infectious Disease rater

This is a useful contribution to some of the glaring issues (gaps) regarding sera-diagnosis of COVID-19 and its implications. However, in view of reported test sensitivity and specificity, it is probably true that test results leaves some tested subjects more sick from unfounded worries. It is time to also think of how best to counteract this spillover along with efforts of searching the best diagnostic test.