Performance of preoperative diagnostic tests for the diagnosis of septic arthritis.
| Diagnostic Test (cutoff value for positive test) | No. Pts with Test Performed | Noninfectious Arthritis, n = 35 | Septic Arthritis, n = 22 | Sensitivity, % (CI 95%) | Specificity, % (CI 95%) | PPV, % (CI 95%) | NPV, % (CI 95%) | Accuracy, % |
|---|---|---|---|---|---|---|---|---|
| Systemic inflammatory markers | ||||||||
| Serum CRP (> 10 mg/l) | 43 | 15/25 | 14/18 | 78 (59–97) | 40 (21–59) | 48 (30–67) | 71 (48–95) | 56 |
| WBC count (> 10 G/l) | 48 | 7/27 | 13/21 | 62 (41–83) | 74 (58–91) | 65 (44–86) | 71 (55–88) | 69 |
| Synovial fluid | ||||||||
| Leukocytes (> 50,000/µl) or granulocytes (> 90%) | 46 | 0/30 | 15/16 | 94 (82–105) | 100 (100) | 100 (100) | 97 (91–103) | 98 |
| Culture | 57 | 0/35 | 10/22 | 46 (25–66) | 100 (100) | 100 (100) | 74 (62–87) | 79 |
| PCR | 57 | 3/35 | 5/22 | 23 (5–40) | 91 (82–100) | 63 (29–96) | 65 (52–79) | 65 |
| Microcalorimetry | 57 | 2/35 | 10/22 | 46 (25–66) | 94 (87–101) | 83 (62–104) | 73 (60–86) | 75 |
Where the denominator is shown, the test was not performed in all patients. PPV: positive predictive value; NPV: negative predictive value; CRP: C-reactive protein; WBC: white blood cell.