Abstract
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.
Highlights
As of today (27 August 2020), the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)has infected 23.980.044 individuals, caused 820.763 deaths, and has spread to virtually all countries [1].Italy has been the first affected country in Europe and one of the most affected worldwide
For whom the final diagnosis remained doubtful after reassessment, were tested with an additional ELISA Anti-SARS-CoV-2 IgG test (Abbott), performed six to eight weeks after the first diagnosis
Early in the course of the epidemic, we realized that a number of patients who resulted positive at the first-line screening test (E target) but negative at the confirmatory test (RdRp target), and who would have been classified as non-infected with SARS-CoV2, were most probably true positives, and we started managing patients
Summary
As of today (27 August 2020), the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)has infected 23.980.044 individuals, caused 820.763 deaths, and has spread to virtually all countries [1].Italy has been the first affected country in Europe and one of the most affected worldwide. Has infected 23.980.044 individuals, caused 820.763 deaths, and has spread to virtually all countries [1]. The diagnosis of SARS-CoV-2 infection is based on standardized molecular methods, usually performed on nasal/pharyngeal swabs [5]. Sensitivity, for instance, depends on the method itself [6], the correct execution of the nasal and pharyngeal swab [7], and the passage of time since exposure and onset of symptoms [8,9,10]. False-negative results may cause mismanagement and nosocomial or community transmission [11,12]. Specificity and positive and negative predictive value (PPV and NPV) of molecular and serological tests for the diagnosis of SARS-CoV-2 infection
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