Diagnostic accuracy of foot length to identify preterm (<37 week) infants, by world region
| Author (year) | Country | GA reference standard | N | % Preterm | Definition of preterm (weeks) | Foot length cut-off (cm) | Sensitivity (%)* | Specificity (%)* | PPV (%) | NPV (%) | AUC* |
| Asia | |||||||||||
| Lee28 (2016)† | Bangladesh | Ultrasound | 710 | 8.3 | <37 | <7.5 | 64 | 35 | 8 | 92 | 0.5191 |
| KC29 (2015)† | Nepal | LMP | 811 | 6.7 | <37 | 7.8 | 76.9 | 53.9 | 10.6 | 97.0 | 0.683 (95% CI 0.610 to 0.756) |
| Pratinidhi30 (2017) | India | LMP | 645 | 6.7‡ | <34 | <6.8 | 93.0 (95% CI 80.9 to 98.5) | 86.7 (95% CI 83.7 to 89.3) | – | – | 0.943 |
| 16.1‡ | <37 | <7.0 | 81.7 (95% CI 73.0 to 88.6) | 80.8 (95% CI 77.2 to 84.0) | – | – | 0.891 | ||||
| Singhal23 (2014) | India | LMP and ‘extended’ NBS | 1000 | 15.4‡ | <34 | 7 | 94.76 | 94.3 | 81.55 | 98.54 | – |
| Mukherjee35 (2013)† | India | NBS | 351 | 48.1 | <37 | <7.75 | 92.3 | 86.3 | – | – | – |
| Roy31 (2019) | India | NBS | 320 | 17.5 | <37 | 7.35 | 80 | 78 | – | – | 0.772 |
| Srinivasa36 | India | NBS | 500 | 16.8 | <37 | <7.4 | 98.81 (95% CI 93.5 to 100.0) | 79.09 (95% CI 74.9 to 82.9) | – | – | – |
| Thi12 (2015) | Vietnam | NBS | 485 | 47 | <37 | <7.3 | 80 (95% CI 74 to 85) | 81 (95% CI 76 to 86) | 79 (95% CI 73 to 84) | 82 (95% CI 77 to 87) | 0.88 (95% CI 0.85 to 0.91) |
| Africa | |||||||||||
| Gidi34 (2020) | Ethiopia | NBS | 1389 | 10.2 | <37 | <7.5 | 81.7 (95% CI 74.3 to 87.7) | 77.0 (95% CI 74.6 to 79.3) | 28.6 (95% CI 24.3 to 33.3) | 97.4 (95% CI 96.2 to 98.3) | 0.86 (95% CI 0.84 to 0.88) |
| Eregie examination | 1389 | 5.5 | <37 | <7.4 | 80.5 (69.9–88.7) | 91.4 (89.7–92.8) | 35.2 (28.2–42.8) | 98.8 (98.0–99.3) | 0.93 (0.91–0.94) | ||
| Marchant37 (2010) | Tanzania | Eregie examination | 529 | 9 | <37 | <8 | 93 (95% CI 82 to 99) | 58 (95% CI 53 to 62) | 15 | 99 | – |
| Nabiwemba 32 (2013a)† | Uganda | Eregie examination | 711 | 4 | <37 | 7.5 | 85.7 | 90.4 | 27.0 | 99.4 | 0.95 |
| 8.0 | 96.4 | 66.2 | 10.6 | 99.8 | |||||||
| Paulsen 33 (2019) | Tanzania | Ultrasound | 376 | 4.5 | <37 | <7.45 | 88 (95% CI 64 to 99) | 85 (95% CI 81 to 88) | 21 (95% CI 13 to 33%) | 99 (95% CI 98 to 100%) | 0.9358 |
| <7.7 | 94 (95% CI 71 to 100) | 64 (95% CI 59 to 69) | 11 (95% CI 6 to 17%) | 100 (95% CI 98 to 100%) | |||||||
(-) symbol indicates that data is not available for that paper.
*Sensitivity/specificity data were converted to a % if in decimal form, and AUC was converted to decimal form if reported as a per cent.
†Paper also reported diagnostic accuracy data for other foot length cut-offs.
‡Per cent calculated by authors (LVF, PP and ACL) from data reported in the paper.
AUC, area under the curve; GA, gestational age; LMP, last menstrual period; NBS, New Ballard Score; NPV, negative predictive value; PPV, positive predictive value; US, ultrasound.