Table 2.
Discriminatory performance of procalcitonin and C-reactive protein for detection of bacterial coinfection, using different cut-off points (N = 4076)
| Variables | Sensitivity% (95% CI) | Specificity% (95% CI) | PPV% (95% CI) | NPV% (95% CI) | LR + (95% CI) | LR– (95% CI) |
|---|---|---|---|---|---|---|
| PCT cut-off | ||||||
| ≥ 0.1 ng/mL | 85 (78.5–91.4) | 18.9 (17.7–20.2) | 3.4 (2.8–4.1) | 97.4 (96.2–98.6) | 1.05 (0.97–1.13) | 0.79 (0.53–1.2) |
| ≥ 0.12 ng/mLa | 81.2 (74.2–88.2) | 24.9 (23.5–26.3) | 3.5 (2.9–4.2) | 97.5 (96.5–98.5) | 1.08 (0.99–1.18) | 0.75 (0.53–1.08) |
| ≥ 0.25 ng/mL | 59.4 (50.7–68.1) | 49.5 (47.9–51) | 3.8 (3–4.7) | 97.3 (96.6–98) | 1.18 (1.02–1.36) | 0.82 (0.67–1.01) |
| ≥ 0.5 ng/mL | 35.3 (26.8–43.8) | 69.3 (67.8–70.7) | 3.7 (2.7–4.8) | 97 (96.3–97.6) | 1.15 (0.91–1.45) | 0.93 (0.82–1.06) |
| ≥ 1 ng/mL | 18.1 (11.1–25) | 91.6 (90.8–92.5) | 6.8 (4–9.5) | 97.1 (96.5–97.6) | 2.16 (1.48–3.14) | 0.89 (0.83–0.97) |
| CRP cut-off | ||||||
| ≥ 10 mg/L | 100 (99.6–100) | 1.9 (1.5–2.3) | 3.3 (2.8–3.9) | 100 (99.3–100) | 1.02 (1.01–1.02) | – |
| ≥ 20 mg/L | 97.7 (94.8–100) | 4.4 (3.8–5.1) | 3.3 (2.8–3.9) | 98.3 (96.1–100) | 1.02 (1–1.05) | 0.51 (0.17–1.58) |
| ≥ 97 mg/La | 80.5 (73.3–87.6) | 36.3 (34.8–37.8) | 4.1 (3.3–4.9) | 98.2 (97.5–98.9) | 1.26 (1.16–1.38) | 0.54 (0.38–0.76) |
| ≥ 100 mg/L | 79.7 (72.5–86.9) | 37.9 (36.3–39.4) | 4.2 (3.4–4.9) | 98.2 (97.5–98.9) | 1.28 (1.17–1.4) | 0.54 (0.38–0.75) |
| ≥ 200 mg/L | 39.9 (31.2–48.6) | 71.7 (70.3–73.1) | 4.5 (3.3–5.8) | 97.3 (96.6–97.9) | 1.41 (1.14–1.75) | 0.84 (0.73–0.96) |
CI confidence interval, PPV positive predictive value, NPV negative predictive value, LR+ positive likelihood ratio, LR– negative likelihood ratio
aCut-off value obtained from ROC curve for bacterial coinfection (value with a sensitivity of 80%)