| Criterion | No (%) patients | Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) | RR (95% CI) |
| Respiratory rate ⩾30/min | 80 (6.4) | 19.7 | 95.8 | 45.0 | 87.3 | 3.56 (2.67 to 4.73) |
| Pao2/Fio2 ⩽250 mm Hg | 296 (23.8) | 70.5 | 84.2 | 43.6 | 94.3 | 7.64 (5.72 to 10.20) |
| Multilobar infiltrates | 480 (38.6) | 71.6 | 67.0 | 27.3 | 93.2 | 4.00 (2.96 to 5.40) |
| Confusion | 221 (17.8) | 57.4 | 89.0 | 47.5 | 92.4 | 6.22 (4.82 to 8.02) |
| BUN >7 mmol/l | 482 (38.8) | 73.2 | 67.1 | 27.8 | 93.6 | 4.31 (3.17 to 5.86) |
| WBC <4000 | 46 (3.7) | 9.3 | 97.3 | 37.0 | 86.1 | 2.66 (1.78 to 3.98) |
| Platelet <100000 | 34 (2.7) | 5.5 | 97.7 | 29.4 | 85.7 | 2.05 (1.20 to 3.52) |
| Temperature <36°C | 38 (3.1) | 9.8 | 98.1 | 47.4 | 86.3 | 3.46 (2.40 to 4.97) |
| Hypotension | 376 (30.3) | 48.1 | 72.8 | 23.4 | 89.0 | 2.13 (1.64 to 2.78) |
BUN, blood urea nitrogen; ; CI, confidence interval; Fio2, fraction of inspired oxygen; NPV, negative predictive value; Pao2, arterial oxygen tension; PPV, positive predictive value; RR, relative risk; WBC, white blood cell.