Test characteristics of screening to predict methicillin resistance in clinical isolates of Staphylococcus aureus, stratified by sterility of site, intensive care unit admission at the time of isolate collection, and screening swab and isolate collection on same admission
| Characteristic | Site of isolate collection | Admission | Screening swab and isolate collection | |||
|---|---|---|---|---|---|---|
| Sterile | Nonsterile | ICU | Non-ICU | Same admission | Different admission | |
| True positive, no. | 5 | 45 | 17 | 33 | 43 | 7 |
| True negative, no. | 97 | 331 | 179 | 249 | 365 | 63 |
| False positive, no. | 1 | 2 | 0 | 3 | 1 | 2 |
| False negative, no. | 6 | 23 | 11 | 18 | 20 | 9 |
| Sensitivity, % (95% CI) | 45 (17–77) | 66 (54–77) | 61 (41–79) | 65 (50–78) | 68 (55–79) | 44 (31–62) |
| Specificity, % (95% CI) | 99 (94–100) | 99 (98–100) | 100 (98–100) | 99 (97–100) | 99 (98–100) | 97 (89–100) |
| Positive likelihood ratio (95% CI) | 45 (5.7–348) | 111 (27–443) | –* | 54 (17–170) | 250 (35–1782) | 14 (3.3–62) |
| Negative likelihood ratio (95% CI) | 0.55 (0.32–0.95) | 0.34 (0.24–0.47) | 0.39 (0.21–0.6) | 0.36 (0.25–0.52) | 0.32 (0.22–0.46) | 0.58 (0.38–0.9) |
| Positive predictive value, % (95% CI) | 83 (36–100) | 96 (86–100) | 100 (80–100) | 92 (77–98) | 98 (88–100) | 78 (40–97) |
| Negative predictive value, % (95% CI) | 94 (88–98) | 94 (90–96) | 94 (90–97) | 93 (90–96) | 95 (92–97) | 88 (78–94) |
CI = confidence interval, ICU = intensive care unit.
↵* Test characteristics could not be calculated owing to high specificity values.