Body Mass Index screening in Children and adolescents, done in a scientific way.
Fabulous article. Although it’s based in Australia, one of its conclusions is that the CDC overweight criteria for Americans, is also suitable for Australia.
The article supports the CDC criteria for children, using the 85th percentile of BMI for defining "at risk of overweight" and the 95th percentile for defining "obesity".
Actually, they did their testing using the NHANES 1 dataset as their 85th and 95th percentile standards.. but as this article shows, the NHANES 1 dataset is extremely close to the current CDC standards.
This fine article provided lots of data tables and charts, showing the ROC curves, the sensitivity and specificity, of choosing various Body-mass index cutoff thresholds. Here is their conclusion:
| Boys | Girls | |||
|---|---|---|---|---|
| Sensitivity | Specificity | Sensitivity | Specificity | |
| 85th percentile | 72% | 95% | 85% | 93% |
| 95th percentile | 33% | 98% | 46% | 100% |
The 85th percentile threshold seems to have excellent diagnostic performance. The 95th percentile threshold may be a little too high, and if it were lowered a little, it would gain some sensitivity without losing too much specificity.
I share their beliefs about choosing the correct balance between sensitivity and specificity:
"Being labeled as overweight may have a significant psychological effect on the child concerned, so clinicans involved in screening may prefer to sacrifice some sensitivity to achieve a low false-positive rate. This compromise will result in some overweight individuals being missed by the screening program, but this seems reasonable in the absence of good longitudinal data on which to base any estimates of the long-term health consequences of excess adopisity and inview of the limited options for effective intervention".
I believe the same principle also applies to adults, that specificity should be high (above 90%), even if means lowering sensitivity somewhat.
