Table 2.
Accuracy of BMI-based cut-offs for obesity* screening
| Age | Criteria | Boys | Girls | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sensitivity | % | Specificity | % | κ† | % se | Sensitivity | % | Specificity | % | κ† | % se | ||
| 7–10 years | IOTF | 74·6 | 72·0–77·1 | 98·2 | 97·7–98·7 | 0·78 | 0·76–0·80 | 85·8 | 80·9–89·7 | 96·0 | 95·3–96·6 | 0·69 | 0·65–0·73 |
| WHO | 74·5 | 71·9–77·0 | 98·3 | 97·8–98·7 | 0·78 | 0·76–0·80 | 72·8‡ | 67·0–77·9 | 98·2 | 97·7–98·6 | 0·72 | 0·68–0·76 | |
| WGOC | 68·4‡ | 65·6–71·0 | 98·4 | 98·0–98·8 | 0·73§ | 0·71–0·76 | 84·0 | 78·9–88·0 | 96·0 | 95·2–96·6 | 0·68 | 0·63–0·72 | |
| 11–14 years | IOTF | 66·7 | 62·3–70·9 | 99·5 | 99·0–99·8 | 0·74 | 0·70–0·78 | 47·9 | 42·0–53·9 | 99·5 | 98·8–99·8 | 0·58 | 0·53–0·64 |
| WHO | 55·8‡ | 51·2–60·3 | 99·6 | 99·1–99·9 | 0·64§ | 0·60–0·68 | 25·5‡ | 20·7–31·1 | 99·9 | 99·4–100·0 | 0·35§ | 0·29–0·41 | |
| WGOC | 49·7‡ | 45·1–54·3 | 99·6 | 99·1–99·9 | 0·59§ | 0·54–0·63 | 39·9‡ | 34·2–45·8 | 99·6 | 99·3–99·9 | 0·51 | 0·45–0·56 | |
| 15–17 years | IOTF | 92·4 | 82·5–97·2 | 92·4 | 89·0–94·8 | 0·75 | 0·66–0·83 | 76·7 | 61·0–87·7 | 100·0 | 98·6–100·0 | 0·85 | 0·77–0·94 |
| WHO | 71·2‡ | 58·6–81·4 | 99·4 | 97·8–99·9 | 0·79 | 0·70–0·88 | 32·6‡ | 19·5–48·7 | 100·0 | 98·6–100·0 | 0·46§ | 0·30–0·62 | |
| WGOC | 77·3‡ | 65·0–86·3 | 96·6 | 94·0–98·2 | 0·75 | 0·66–0·84 | 67·4 | 51·3–80·5 | 100·0 | 98·6–100·0 | 0·79 | 0·68–0·89 | |
IOTF, International Obesity Task Force; WGOC, Working Group of Obesity in China.
*
Calculated using body fat percentage cut-off points of 25 % in all boys, 30 % in girls aged 7–14 years and 35 % in girls aged 15–17 years.
†
Significant κ statistic, all κ yielded P < 0·001.
‡
Statistically significant difference in sensitivity from IOTF in the same subgroup, P < 0·01 (McNemar’s test).
§
Statistically significant difference in κ value from IOTF in the same subgroup, P < 0·001 (z test).