Current best evidence for clinical care (more info)
BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has had a devastating impact worldwide, and timely detection and quarantine of infected patients are critical to prevent spread of disease. Serological antibody testing is an important diagnostic method used increasingly in clinics, although its clinical application is still under investigation.
METHODS: A meta-analysis was conducted to compare the diagnostic performance of severe acute respiratory syndrome coronavirus-2 antibody tests in patients with COVID-19. The test results analysed included: (1) IgM-positive but IgG-negative (IgM+IgG-); (2) IgG-positive but IgM-negative (IgG+IgM-); (3) both IgM-positive and IgG-positive (IgM+IgG+); (4) IgM-positive without IgG information (IgM+IgG+/-); (5) IgG-positive without IgM information (IgG+IgM+/-); (6) either IgM-positive or IgG-positive (IgM+ or IgG+); and (7) IgA-positive (IgA+).
RESULTS: Sixty-eight studies were included. Pooled sensitivities for IgM+IgG-, IgG+IgM-, IgM+IgG+, IgM+IgG+/-, IgG+IgM+/-, and IgM+ or IgG+ were 6%, 7%, 53%, 68%, 73% and 79% respectively. Pooled specificities ranged from 98% to 100%. IgA+ had a pooled sensitivity of 78% but a relatively low specificity of 88%. Tests conducted 2 weeks after symptom onset showed better diagnostic accuracy than tests conducted earlier. Chemiluminescence immunoassay and detection of S protein as the antigen could offer more accurate diagnostic results.
DISCUSSION: These findings support the supplemental role of serological antibody tests in the diagnosis of COVID-19. However, their capacity to diagnose COVID-19 early in the disease course could be limited.
| Discipline / Specialty Area | Score |
|---|---|
| Emergency Medicine | |
| Infectious Disease | |
| Family Medicine (FM)/General Practice (GP) | |
| General Internal Medicine-Primary Care(US) | |
| Hospital Doctor/Hospitalists | |
| Internal Medicine | |
These results suggest that antibody testing is of limited value in the acute phase of suspected COVID-19 illness. With wide availability of PCR testing, antibody tests are relegated more to being tests of prior exposure than acute illness.
Antibody tests have little clinical relevance. They are not useful in diagnosing acute disease and should primarily be used in epidemiologic studies assessing population rates of infection.
This is a valuable review of the use cases for serology in the diagnosis of COVID-19; the methods are clear, and summarize current understanding well. However, the end result is still that this is of questionable value in isolation, and other tests are likely to be needed for most real-world scenarios.