Diagnostic performance of Standard™Q COVID-19 Ag
As shown in Table 2 and Figure 1 , out of the 69 RT-qPCR positive subjects, 54 were positive by the RAT (sensitivity = 78.2%). Of the 14 RT-qPCR negative subjects, nine were negative by the RAT (specificity = 64.2%). The RAT revealed 15 and 5 false negative and false positive subjects, respectively. The accuracy (overall concordance rate) of the RAT tests was 75.9%. Overall, the results of RT-qPCR and the RAT correlated weakly positive (r = 0.3, P-value = 0.005) and agreed fairly [Cohen’s kappa (κ) = 0.3 (CI = 0.16-0.59), SD = 0.1,P-value = 0.0006)] in a significant manner. The Ctvalues were significantly different (P-value < 0.0001) between RAT positive and negative subjects. The RAT showed the highest sensitivity (96.5%), specificity (44%) and accuracy (63.2%) in COVID-19 patients that have the highest viral nucleic acid content (Ct values < 29) compared to the groups with the lower viral load (Ct values ≥ 29). Other measures for accuracy for subject’s subgroups based on Ct values are shown inTable S2. The ROC analysis yielded an AUC value of 0.7 ±0.08 (Ci = 0.0.5-0.8, P -value = 0.02) (Figure 2 A) .