Diagnostic accuracy of Ballard, LMP and AMANHI models for identification of newborns <37 and <34 weeks (gold standard dated by early pregnancy ultrasound)
| Model | Area under the curve | Cut-off selection | Sensitivity | Specificity | Positive predictive value | Negative predictive value | Positive likelihood ratio | Negative likelihood ratio |
| Classify <37 weeks* | ||||||||
| LMP (<37 weeks)† | 0.81 | LMP <37 weeks cut-off | 0.69 | 0.81 | 0.22 | 0.97 | 3.72 | 0.38 |
| LMP | 0.81 | 80% sensitivity | 0.80 | 0.71 | 0.18 | 0.98 | 2.78 | 0.28 |
| Ballard exam‡ | 0.74 | BS cut-off <37 weeks | 0.09 | 0.98 | 0.25 | 0.93 | 4.29 | 0.93 |
| Ballard exam | 0.74 | 80% sensitivity | 0.80 | 0.52 | 0.12 | 0.97 | 1.68 | 0.38 |
| Model A (10-characteristics) | 0.88 | 80% sensitivity | 0.80 | 0.80 | 0.23 | 0.98 | 3.93 | 0.25 |
| Model B (10-characteristics+LMP) | 0.91 | 80% sensitivity | 0.80 | 0.87 | 0.32 | 0.98 | 5.96 | 0.23 |
| Model C (BW+LMP) | 0.88 | 80% sensitivity | 0.80 | 0.80 | 0.23 | 0.98 | 3.95 | 0.25 |
| Model D (BW+HC) | 0.84 | 80% sensitivity | 0.80 | 0.72 | 0.18 | 0.98 | 2.85 | 0.28 |
| Classify <34 weeks§ | ||||||||
| LMP¶ | 0.94 | LMP <34 weeks cut-off | 0.61 | 0.95 | 0.10 | 1.00 | 12.93 | 0.41 |
| LMP | 0.94 | 80% sensitivity | 0.80 | 0.90 | 0.07 | 1.00 | 8.05 | 0.22 |
| Ballard** | 0.89 | BS cut-off <34 weeks | 0.03 | 1.00 | 0.40 | 0.99 | 74.36 | 0.97 |
| Ballard | 0.89 | 80% sensitivity | 0.80 | 0.81 | 0.04 | 1.00 | 4.13 | 0.25 |
| Model A (10-characteristics) | 0.94 | 80% sensitivity | 0.80 | 0.96 | 0.16 | 1.00 | 21.38 | 0.21 |
| Model B (10- characteristics+LMP) | 0.96 | 80% sensitivity | 0.80 | 0.98 | 0.31 | 1.00 | 50.39 | 0.20 |
| Model C (BW+LMP) | 0.96 | 80% sensitivity | 0.80 | 0.98 | 0.23 | 1.00 | 34.24 | 0.20 |
| Model D (BW+HC) | 0.93 | 80% sensitivity | 0.80 | 0.93 | 0.10 | 1.00 | 12.23 | 0.21 |
Diagnostic accuracy for different cut-offs with preset sensitivity of 85%, 90% and 95% are shown in online supplemental table 2.
*In the cohort there were 536 infants that were classified as preterm <37 weeks, and 6892 classified as ≥37 weeks.
†LMP <37 weeks was classified as preterm, and LMP ≥37 weeks classified as full term.
‡GA as determined by Ballard score was classified as preterm if GA <37 weeks using the equation GA=((2×score)+120))/5.
§In the cohort there were 66 infants that were classified as preterm <34 weeks, and 7362 classified as ≥34 weeks.
¶Threshold of GA determined by LMP <34 weeks.
**Original Ballard score equation (as per footnote 3) classification.
AMANHI, Alliance for Maternal and Newborn Health Improvement; BS, Ballard Score; BW, birth weight; GA, gestational age; HC, head circumference; LMP, last menstrual period.