The Challenge of Using an Antigen Test as a Screening Tool for SARS-CoV-2 Infection in an Emergency Department: Experience of a Tertiary Care Hospital in Southern Italy

Table 4

Sensitivity, specificity, positive predictive value, negative predictive value, and concordance (%) of the CLEIA antigen test according to clinical picture and number of days postsymptom onset.

	Sensitivity (95% CI)	Specificity (95% CI)	PPV (95% CI)	NPV (95% CI)	Concordance ()
All patients enrolled	94.9 (91.9–97.0)	97.4 (96.5–98.1)	91.9 (89.0–94.0)	98.4 (97.4–99.1)	96.8 (882/911)
Asymptomatic	91.8 (81.9–97.2)	97.8 (96.8–98.3)	80.4 (71.7–85.0)	99.2 (98.2–99.7)	97.3 (535/550)
Symptomatic	95.8 (92.7–97.7)	96.4 (93.7–98.0)	95.8 (92.7–97.7)	96.4 (93.7–98.0)	96.1 (347/361)
≤7 days	97.3 (93.4–99.1)	97.1 (94.1–98.6)	96.4 (92.6–98.2)	97.8 (94.8–99.3)	97.2 (242/249)
>7 days	93.6 (86.2–97.0)	89.5 (71.2–97.8)	95.7 (88.1–99.1)	85.0 (67.7–93.0)	92.4 (61/66)

Sensitivity: (CLEIA+ RT-qPCR+)/RT-qPCR+; specificity: (CLEIA- RT-qPCR-)/RT-qPCR-; PPV (positive predictive value): (CLEIA+ RT-qPCR+)/CLEIA+; NPV (negative predictive value): (CLEIA- RT-qPCR-)/CLEIA-; concordance: (CLEIA+ RT-qPCR+) + (CLEIA- RT-qPCR-)/(CLEIA+ RT-qPCR+) + (CLEIA- RT-qPCR-) + (CLEIA+ RT-qPCR-) + (CLEIA- RT-qPCR+).