Accuracy of POC CRP at different thresholds to diagnose serious infection
| POC CRP threshold | Sensitivity (95% CI) | Specificity (95% CI) | Likelihood ratio (95% CI) | Predictive value (95% CI) | ||
| negative | positive | negative | positive | |||
| ≥5 mg/L | 90.8 (86.6 to 94.0) | 33.4 (32.0 to 34.7) | 0.3 (0.2 to 0.4) | 1.4 (1.3 to 1.4) | 98.5 (97.7 to 99.0) | 7.1 (6.3 to 8.0) |
| ≥20 mg/L | 73.1 (67.2 to 78.4) | 63.9 (62.5 to 65.2) | 0.4 (0.3 to 0.5) | 2.0 (1.9 to 2.2) | 97.7 (97.1 to 98.2) | 10.2 (8.9 to 11.7) |
| ≥80 mg/L | 35.0 (29.2 to 41.1) | 94.8 (94.1 to 95.4) | 0.7 (0.6 to 0.8) | 6.7 (5.5 to 8.2) | 96.3 (95.7 to 96.8) | 27.3 (22.6 to 32.5) |
| ≥200 mg/L | 9.6 (6.3 to 13.9) | 99.7 (99.5 to 99.9) | 0.9 (0.9 to 0.9) | 37.1 (18.9 to 37.1) | 95.2 (94.5 to 95.7) | 67.6 (50.2 to 82.0) |
All diagnostic characteristics are given in percentage with their respective 95% CIs in brackets.
POC CRP, point-of-care C reactive protein test.