Agreement analysis among measures of thinness and obesity assessment in Iranian school children and adolescents

This study investigated the agreement of four anthropometric-based measurements including weight-for-height (WH), body mass index-for-age (BMI), mid-upper arm circumference-for-age (MUAC), and triceps skinfold thickness-for-age (TST) to identify underweight and overweight children and adolescents. Two data sets were used in this research. The first one was a multistage random sample of 2397 healthy school children in pre-pubertal stage in Shiraz. The second data set consisted of 487 healthy students in pubertal stage and 558 students in post-pubertal stage. The parametric LMS method was used to construct reference centiles curves for each measure. The Kappa statistic was applied to examine the pairwise agreement of the four indices for detecting thinness and obesity. Generally, the pairwise agreement of adiposity measures was higher for identifying obesity than thinness. There was an excellent agreement between WH and BMI for detecting both thin and obese children in almost all subgroups. MUAC had an excellent agreement with BMI in pre-pubertal individuals. However, TST had a weak agreement with the other three indices for detecting thinness and weak to good agreement for classification of obesity. Based on our findings, the performance of the four anthropometric-based measurements varied by sex and maturity level. Therefore, researchers should be more careful while using these indicators to define thin and obese individuals in different subgroups. MUAC as a simple and low-cost screening tool can also be used as an alternative to BMI for obesity assessment among pre-pubertal groups. However, TST should be used cautiously with the other body composition indices.