Receiver operating characteristic (ROC) curve analysis in 5-10-year-old Bengalee girls from Calcutta, India

Abstract

Objective: The purpose of the present cross-sectional study was to evaluate the sensitivity (SN) and specificity (SP) of body mass index (BMI) and skinfolds thickness: BMI (subcutaneous to overall fat) in detecting excess adiposity in pre-menarcheal Bengalee girls.

Methods: Four hundred and fifty Bengalee girls aged 7.4 +/- 1.16 years (mean +/- SD; range: 5-10 years) from Calcutta were studied. Anthropometric measures--namely height, weight, circumference of mid upper arm, waist and hip, and skinfold thickness at biceps, triceps, subscapular and suprailiac - were taken from all participants using standard protocols. BMI and the log-transformed sum of four (biceps, triceps, subscapular, suprailiac) skinfolds (log10 SF4) were computed subsequently. Values of log10 SF4 were then converted into seven percentiles category (5th, 10th, 25th, 50th, 75th, 85th and 95th). Excess adiposity was defined as a level of log10 SF4 greater than the internally derived 85th percentile (log10 SF4>85th percentile). SN and SP of each internally derived percentile of BMI and log10 SF4:BMI in detecting excess adiposity were then computed.

Results: SN and SP were 0.49 and 0.94 for the 95th percentile of BMI, and 0.76 and 0.82 for the 95th percentile of log10 SF4:BMI. Moreover, there was a considerable decrease in overall misclassification with the use of log10 SF4:BMI instead of BMI at the 95th percentile (11.2% vs 32%).

Conclusion: Percentiles of BMI in the study had higher SP but low SN in detecting excess adiposity. The use of log10 SF4:BMI, on the other hand, had the merit of increasing SN in a screening programme to evaluate excess adiposity in Bengalee children aged 5-10 years.