This document provides guidance for health care providers regarding diagnostic tests for SARS-CoV-2, the virus causing COVID-19 disease. While serologic tests are becoming more widely available, no serologic tests are currently approved by the FDA for diagnosing COVID-19. Reverse transcriptase-polymerase chain reaction (RT-PCR) tests remain the preferred tests for diagnosing COVID-19 in individual patients.
Serologic tests should generally not be used to diagnose acute cases of COVID-19 or to infer immunity, because:
There is a high degree of variability in sensitivity and specificity between different serologic assays. Serologic tests are generally less specific than RT-PCR tests and have a greater potential to cross-react with Coronaviruses other than SARS-CoV-2. Remember that the positive predictive value of a test depends on not only the sensitivity and specificity of a test, but also on prevalence of disease. In a population with a 5% prevalence of SARS-CoV-2 infection, a serologic test with 95% sensitivity and 95% specificity will have 50% positive predictive value.
FIND SARS-CoV-2 DiagnosticsIDSA COVID-19 Antibody Testing Primer (PDF)Johns Hopkins Center for Health Security – Serology-based tests for COVID-19 Johns Hopkins Center for Health Security – Developing a National Strategy for Serology (Antibody Testing) in the United States