Sensitivity, Specificity and Predictive Values of the Rapid Antigen Diagnosis Test of SARS-CoV-2 Virus Panbio COVID-19 at the Patient Screening Point of Hospital Geral De Luanda, Angola

Abstract Introduction: Alternative forms of diagnosis that are simpler than NAAT and with faster results (15–30 min) were developed based on the direct detection of SARS-CoV-2 viral proteins in nasal swabs and other respiratory tract secretions using a lateral flow immunoassay also called a rapid diagnostic test of antigen detection. The WHO recommends that these tests have at least a sensitivity of 80% and a specificity of 97% when compared to the reference test, the RT-PCR. We evaluated the performance of the rapid antigen detection test Panbio COVID-19 at a patient triage point at the Luanda General Hospital. Methods: A cross-sectional study of a prospective nature was carried out with the inclusion of 37 suspected symptomatic cases without a previous diagnosis of COVID-19. The database was created and processed in MedCal version 19.6. Sensitivity, specificity, positive and negative predictive value and accuracy are expressed in percentages with the respective 95% confidence intervals determined using a 2x2 table. Qualitative variables were presented in absolute and relative frequency. The McNemar's test was used to calculate the proportion of RAD test results Panbio COVID-19 in relation to the RT –PCR and a bilateral P value < 0.05 calculated based on the cumulative binomial distribution was considered significant. Results: In our study, 26 (70.3%) of the cases were male, and the mean age was 18 years, with a standard deviation of 14.8, with 14 (37.8%) residing in the municipality of Talatona. Regarding the days of evolution of symptoms, 34 (91.9%) had symptoms with one week of evolution. The RAD test Panbio COVID-19 had a sensitivity of 54.5% (CI 95% 23.3 – 83.2) and specificity of 96.1% (CI 95% 80.3 – 99.9). The positive and negative predictive value was 85.7% (95% CI 44.9 – 97.7) and 83.3% (95% CI 72.2– 90.5) respectively. The accuracy of the test was 83.7% (95% CI 67.9 – 93.8). The difference between the prevalence in the test Panbio COVID-19 and in RT-PCR it was 10.8% (95% CI -1.6 – 23.3), not being statistically significant (P=0.22). As for the cycle threshold, 71.4% of the samples that were positive for RAD test Panbio COVID-19 had a cycle threshold ≤ 25. Conclusion: The RAD test Panbio COVID-19 did not meet the minimum accuracy requirements recommended by the WHO. However, the predictive values were considerably high in symptomatic subjects.