Current best evidence for clinical care (more info)
BACKGROUND: We assessed the sensitivity, specificity and positive and negative predictive value (PPV and NPV) of molecular and serological tests for the diagnosis of SARS-CoV-2 infection.
METHODS: A total of 346 patients were enrolled in the emergency room. We evaluated three Reverse Transcriptase-real time PCRs (RT-PCRs) including six different gene targets, five serologic rapid diagnostic tests (RDT) and one ELISA. The final classification of infected/non-infected patients was performed using Latent Class Analysis combined with clinical re-assessment of incongruous cases.
RESULTS: Out of these, 24.6% of patients were classified as infected. The molecular test RQ-SARS-nCoV-2 showed the highest performance with 91.8% sensitivity, 100% specificity, 100.0% PPV and 97.4% NPV respectively. Considering the single gene targets, S and RdRp of RQ-SARS-nCoV-2 had the highest sensitivity (94.1%). The in-house RdRp presented the lowest sensitivity (62.4%). The specificity ranged from 99.2% for in-house RdRp and N2 to 95.0% for E. The PPV ranged from 97.1% of N2 to 85.4% of E and the NPV from 98.1% of S to 89.0% of in-house RdRp. All serological tests had < 50% sensitivity and low PPV and NPV. VivaDiag IgM (RDT) had 98.5% specificity, with 84.0% PPV, but 24.7% sensitivity.
CONCLUSION: Molecular tests for SARS-CoV-2 infection showed excellent specificity, but significant differences in sensitivity. Serological tests have limited utility in a clinical context.
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This provides evidence for the sensitivity of the RT-PCR tests that is above what was prior thought in the literature, and also the limitations of serologic testing at this time.
The study reinforces the concept that the serological response to SARS-CoV-2 cannot be defined with the current tests, nor be the basis for diagnosing the infection.
This is a single centre study.
This is a current and clinically relevant study, however the findings should be interpreted in light of the the single-centre design and limited sample size.
This study provides important guidance on test selection in confirming the diagnosis of COVID-19. It's especially important as we enter annual flu season, when symptoms can overlap.