Table 3.
Sensitivity, specificity and predictive values for a rapid antigen detection test (RADT) for group A streptococci (GAS) at different Centor scores
| Centor score | All patients (n = 220) | Patients tested with RADT (n = 207) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| n (%) | Prevalence of GAS in culture n (%) |
Tested n (%) |
Positive n (%) |
Sensitivitya (95% CI) |
Specificitya (95% CI) |
PPVa (95% CI) |
NPVa (95% CI) |
AUCa (95% CI) |
|
| 0 | 16 (7) | 2 (13) | 15 (94) | 3 (20) | 100 (16–100) | 92 (64–100) | 67 (23–93) | 100 | 0.96 (0.86–1.0) |
| 1 | 50 (23) | 6 (12) | 46 (92) | 5 (11) | 50 (12–88) | 95 (83–99) | 60 (24–88) | 93 (85–97) | 0.73 (0.46–0.99) |
| 2 | 69 (31) | 16 (23) | 67 (97) | 18 (27) | 81 (54–96) | 90 (79–97) | 72 (52–86) | 94 (85–98) | 0.86 (0.74–0.98) |
| 3 | 54 (25) | 24 (44) | 52 (96) | 24 (46) | 96 (78–100) | 93 (77–99) | 92 (74–98) | 96 (80–99) | 0.94 (0.87–1.0) |
| 4 | 31 (14) | 18 (58) | 27 (87) | 18 (67) | 100 (80–100) | 90 (56–100) | 94 (73–99) | 100 | 0.95 (0.84–1.0) |
| Total | 220 (100) | 66 (30) | 207 (94) | 68 (33) | 89 (79–95) | 92 (87–96) | 84 (74–90) | 95 (90–97) | 0.91 (0.86–0.96) |
RADT rapid antigen detection test, GAS group A streptococci, PPV positive predictive value (true positives/all positives), NPV negative predictive value (true negatives/all negatives), AUC area under the curve, 95% CI 95% confidence interval
aAll numbers for RADT are calculated with throat culture as reference standard for the detection of group A streptococci