Table 3.
Criterion value and coordinates of ROC curve of 24 h urinary calcium excretion at 16 weeks of gestation
| Criterion 24 h urinary excretion of ‘Ca’ | Sensitivity (%) | Specificity (%) | +LR (%) | −LR (%) | +PV (%) | −PV (%) |
|---|---|---|---|---|---|---|
| ≥70 mg | 100.00 | 0.0 | 1.00 | − | 50.00 | − |
| (88.4–100.00) | (0.0–11.6) | (36.8–63.2) | ||||
| >188 | 76.67 | 83.33 | 4.60 | 0.28 | 82.1 | 78.1 |
| (57.7–90.1) | (65.3–94.4) | (3.6–5.9) | (0.1–0.8) | (62.7–94.1) | (59.7–90.9) | |
| >220 mg* | 73.33 | 96.67 | 22.00 | 0.28 | 95.7 | 78.4 |
| (54.1–87.7) | (82.8–99.9) | (17.6–27.6) | (0.04–2.1) | (77.4–99.9) | (61.8–90.2) | |
| >308 mg | 0.0 | 100.00 | – | 1.00 | – | 50.0 |
| (0.0–11.6) | (88.4–100.0) | (36.8–63.2) |
+LR positive likelihood ratio, −LR negative likelihood ratio, +PV positive predictive value, −PV negative predictive value
Data presented as mean (95 % confidence interval)
* You den’s index (J) = sensitivity + specificity – 1 (=0.73 + 0.97 − 1) = 0.70 (The maximum value ‘J’ can attain is 1 when the test is perfect, and the maximum value is usually 0 when the test has no diagnostic value)