Table 4. Comparison of World Health Organization body mass index-for-age cut-offs for obesity and overweight and the empirically determined optimal cut-off for identifying excessive fatness among children in eight African countries, 2013–2017.
| Diagnostic performance measurea | BMI z-score > +2.00 SD |
BMI z-score > +1.00 SD |
BMI z-score +0.58 SDb |
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|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of children | Total no. | % (95% CI) | No. of children | Total no. | % (95% CI) | No. of children | Total no. | % (95% CI) | |||
| Sensitivity | 131 | 441 | 29.7 (25.5 to 34.2) | 261 | 441 | 59.2 (54.4 to 63.8) | 317 | 441 | 71.9 (67.4 to 76.0) | ||
| Specificity | 1072 | 1075 | 99.7 (99.2 to 99.9) | 1040 | 1075 | 96.7 (95.5 to 97.7) | 979 | 1075 | 91.1 (89.2 to 92.7) | ||
| Positive predictive value | 131 | 134 | 97.8 (93.6 to 99.5) | 261 | 296 | 88.2 (83.9 to 91.6) | 317 | 413 | 76.8 (72.4 to 80.7) | ||
| Negative predictive value | 1072 | 1382 | 77.6 (75.3 to 79.7) | 1040 | 1220 | 85.2 (83.1 to 87.2) | 979 | 1103 | 88.8 (86.7 to 90.6) | ||
BMI: body mass index; CI: confidence interval; SD: standard deviation.
a We calculated values as follows: sensitivity: [true positives/(true positives + false negatives)]; specificity: [true negatives/(true negatives + false positives)]; positive predictive value: [true positives/(true positives + false positives)]; negative predictive value: [true negatives/(true negatives + false negatives)].
b We calculated the optimal cut-off z-score from the receiver operating characteristic curve (area under the curve: 0.86).