Sensitivity, Specificity and Predictive Values of Molecular and Serological Tests for COVID-19: A Longitudinal Study in Emergency Room

• Main Authors: Zeno Bisoffi, Elena Pomari, Michela Deiana, Chiara Piubelli, Niccolò Ronzoni, Anna Beltrame, Giulia Bertoli, Niccolò Riccardi, Francesca Perandin, Fabio Formenti, Federico Gobbi, Dora Buonfrate, Ronaldo Silva
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Diagnostics
• Subjects: SARS-CoV-2; diagnosis; serology; RT-PCR; accuracy
• Online Access: https://www.mdpi.com/2075-4418/10/9/669

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, <i>S</i> and <i>RdRp</i> of RQ-SARS-nCoV-2 had the highest sensitivity (94.1%). The in-house <i>RdRp</i> presented the lowest sensitivity (62.4%). The specificity ranged from 99.2% for in-house <i>RdRp</i> and <i>N2</i> to 95.0% for <i>E</i>. The PPV ranged from 97.1% of <i>N2</i> to 85.4% of <i>E</i> and the NPV from 98.1% of <i>S</i> to 89.0% of in-house <i>RdRp</i>. 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.