Table 4. Diagnostic performance of point of care AF IL-6 concentrations and ELISA AF IL-6 for identification of patients with spontaneous preterm delivery.
| Point of care IL-6 test (cut-off 745 pg/ml) |
ELISA IL-6 (cut-off 2600 pg/ml) |
|||||
|---|---|---|---|---|---|---|
| Outcomes | Diagnostic performance | % (n) | 95% CI | % (n) | 95% CI | |
| Spontaneous preterm delivery within one day after amniocentesis [33.8% (46/136)] | Sensitivity | 84.8 (39/46) | (71.1–93.6) | 78.3 (36/46) | (63.6–89.0) | |
| Specificity | 73.3 (66/90) | (63–82) | 73.3 (66/90) | (63–82.1) | ||
| Positive predictive value | 62 (39/63) | (48.8–73.9) | 60.0 (36/60) | (46.5–72.4) | ||
| Negative predictive value | 90.4 (66/73) | (81.2–96.0) | 86.8 (66/76) | (77.1–93.5) | ||
| Positive likelihood ratio | 3.2 (84.4/26.7) | (2.2–4.6) | 2.9 (78.3/26.7) | (2.0–4.3) | ||
| Negative likelihood ratio | 0.21 (15.2/73.3) | (0.1–0.4) | 0.3 (21.7/73.3) | (0.2–0.5) | ||
| Spontaneous preterm delivery within two days after amniocentesis [43.4% (59/136)] | Sensitivity | 79.7 (47/59) | (67.2–89) | 71.2 (42/59) | (57.9–82.2) | |
| Specificity | 79.2 (61/77) | (68.5–87.6) | 76.6 (59/77) | (65.6–85.5) | ||
| Positive predictive value | 74.6 (47/63) | (62.1–84.7) | 70.0 (42/60) | (56.8–81.2.5) | ||
| Negative predictive value | 83.6 (61/73) | (73–91.2) | 77.6 (59/76) | (66.6–86.4) | ||
| Positive likelihood ratio | 3.8 (79.7/20.8) | (2.4–6) | 3.1 (71.2/23.4) | (2–4.7) | ||
| Negative likelihood ratio | 0.3 (20.3/79.2) | (0.2–0.4) | 0.4 (28.8/76.6) | (0.3–0.6) | ||
| Spontaneous preterm delivery within seven days after amniocentesis [47.8% (65/136)] | Sensitivity | 78.5 (51/65) | (66.5–87.7) | 72.3 (47/65) | (59.8–82.7) | |
| Specificity | 83.1 (59/71) | (72.3–90.9) | 81.69 (58/71) | (70.7–89.9) | ||
| Positive predictive value | 81 (51/63) | (69.1–89.7) | 78.3 (47/60) | (65.8–87.9) | ||
| Negative predictive value | 80.8 (59/73) | (69.9–89.1) | 76.3 (58/76) | (65.2–85.3) | ||
| Positive likelihood ratio | 4.6 (78.5/16.9) | (2.7–7.9) | 4.0 (72.3/18.31) | (2.4–6.6) | ||
| Negative likelihood ratio | 0.3 (21.5/83.1) | (0.16–0.4) | 0.3 (27.7/81.69) | (0.2–0.5) | ||
| Spontaneous preterm delivery <28 weeks [22.8% (31/136)]* | Sensitivity | 87.1 (27/31) | (70–96.3) | 83.9 (26/31) | (66.3–94.5) | |
| Specificity | 75.0 (6/8) | (35.1–96.7) | 75.0 (6/8) | (35.1–96.1) | ||
| Positive predictive value | 93.1 (27/29) | (77.2–99.0) | 92.9 (26/28) | (76.5–98.9) | ||
| Negative predictive value | 60.0 (6/10) | (26.4–87.6) | 54.6 (6/11) | (23.5–83.1) | ||
| Positive likelihood ratio | 3.5 (87.1/25) | (1.04–11.7) | 3.4 (83.9/25) | (1.0–11.3) | ||
| Negative likelihood ratio | 0.2 (12.9/75) | (0.06–0.5) | 0.22 (16.1/75) | (0.09–0.53) | ||
| Spontaneous preterm delivery <34 weeks [54.4% (74/136)]† | Sensitivity | 77.03 (57/74) | (65.8–86.01) | 72.97 (54/74) | (61.4–82.6) | |
| Specificity | 71.43 (5/7) | (29.3–95.5) | 85.71 (6/7) | (42.2–97.6) | ||
| Positive predictive value | 96.6 (57/59) | (88.3–99.5) | 98.2 (54/55) | (90.2–99.7) | ||
| Negative predictive value | 22.7 (5/22) | (7.9–45.4) | 23.08 (6/26) | (90.3–99.7) | ||
| Positive likelihood ratio | 2.7 (77.03/28.57) | (0.8–8.8) | 5.1 (72.97/14.29) | (0.19–0.51) | ||
| Negative likelihood ratio | 0.32 (22.97/71.43) | (0.17–0.6) | 0.32 (27.03/85.71) | (0.19–0.51) | ||
CI: confidence interval.
*The analysis was performed only in patients who had amniocentesis at <28 weeks (n = 39).
†The analysis was performed only in patients who had amniocentesis at <34 weeks (n = 81).