Table 4.
Diagnostic indices of various factors to predict intra-amniotic infection and imminent preterm delivery
| Variables | Area (±SE) under the ROC curve | 95% CI | Cut-off valuea | Sensitivityb (95% CI) |
Specificityb (95% CI) |
PPV | NPV |
|---|---|---|---|---|---|---|---|
| Intra-amniotic infection | |||||||
| Plasma IL-6 (pg/mL) | 0.76 ± 0.07 | 0.63–0.89 | 4.8 | 75.0 (50.1–93.2) | 75.6 (47.6–92.7) | 24.0 | 96.8 |
| AF IL-6 (ng/mL) | 0.98 ± 0.01c | 0.96–1.00 | 3.6 | 100 (79.4–100.0)d | 92.4 (87.0–96.0)d | 57.1 | 100 |
| Serum CRP (mg/L) | 0.81 ± 0.06 | 0.69–0.93 | 11.2 | 62.5 (35.4–84.8) | 86.0 (80.0–91.0)e | 31.3 | 95.7 |
| Cervical length (mm) | 0.66 ± 0.06 | 0.55–0.77 | 20.6 | 62.5 (35.4–84.8) | 65.0 (57.0–72.4)f | 15.4 | 94.4 |
| Imminent preterm delivery | |||||||
| Plasma IL-6 (pg/mL) | 0.77 ± 0.06 | 0.66–0.88 | 4.8 | 73.1 (52.2–88.4) | 78.2 (70.7–84.6) | 37.3 | 94.3 |
| AF IL-6 (ng/mL) | 0.74 ± 0.05 | 0.64–0.85 | 1.5 | 61.5 (40.6–79.8) | 78.2 (70.7–84.6) | 33.3 | 92.0 |
| Serum CRP (mg/L) | 0.68 ± 0.06 | 0.57–0.79 | 3.5 | 88.5 (69.9–97.6) | 51.0 (42.7–59.4)d | 24.2 | 96.2 |
| Cervical length (mm) | 0.81 ± 0.05 | 0.72–0.90 | 20.0 | 76.9 (56.4–91.0) | 71.4 (63.4–78.6) | 32.3 | 94.6 |
SE standard error; ROC receiver-operating characteristic, CI confidence interval, PPV positive predictive value, NPV negative predictive value; IL-6 interleukin-6, AF amniotic fluid, CRP C-reactive protein
aCut-off values corresponding to the highest sum of sensitivity and specificity
bValues are given as % (95% CI)
cP < 0.001 compared to plasma IL-6 by the method of DeLong et al.
dP < 0.001 compared to plasma IL-6 by McNemar’s test
eP < 0.01 compared to plasma IL-6 by McNemar’s test
fP < 0.05 compared to plasma IL-6 by McNemar’s test