Diagnostic performance of anthropometric measurements for identifying obesity in high-altitude pediatric populations: evidence from tibet via bioelectrical impedance analysis.

Abstract

Background: The diagnostic accuracy of anthropometric measurements for obesity screening in high-altitude pediatric populations remains understudied, particularly since existing measurements have been validated predominantly in lowland populations. This study evaluated the effectiveness of 19 anthropometric measurements for obesity screening among youth residing in the Tibetan Plateau region, aiming to identify the most reliable measurement approach for this distinct demographic.

Methods: This study included 1,650 Tibetan and Han Chinese students aged 8-18 years from six schools in Lhasa's Chengguan District (altitude 3,650 m). Anthropometric measurements comprised both basic anthropometric parameters and computed indices. The basic anthropometric parameters included height, weight, waist circumference, mid-upper arm circumference as well as skinfold thickness measured at three sites, such as abdominal skinfold thickness (AST). The computed indices consisted of Body Mass Index (BMI), the tri-ponderal mass index (TMI), the sum of skinfold thickness from two or three (SuST₃) sites, the waist-to-height ratio, the mid-upper arm-to-height ratio, the conicity index (C-index), the relative fat mass, the body roundness index, two variants of a body shape index (ABSI_OR and ABSI_CN), and two percentage body fat values derived from two skinfold thickness equations (such as Y-PBF). Bioelectrical impedance analysis-derived percentage of body fat (PBF_BIA) was used as the reference method to construct Receiver Operating Characteristic (ROC) curves for the 19 anthropometric measurements, and the Area Under the Curve (AUC) was calculated to evaluate the performance of each measurement in obesity screening.

Results: Statistical analysis revealed that TMI, SuST₃, AST, and BMI consistently demonstrated robust correlations with PBF_BIA across all demographic subgroups (p < 0.001, r > 0.7) and exhibited strong diagnostic capabilities (AUC > 0.800). Among all anthropometric measurements, the TMI, SuST₃, AST, Y-PBF, and BMI had the highest subgroup mean rankings according to the AUC (top 5), and the ABSI_OR, C-index, and ABSI_CN were the worst (bottom 3). DeLong's test confirmed these measurements as optimal measures in the majority of population subgroups (> 10 out of 19 subgroups), with the TMI showing the most comprehensive applicability (valid for the total sample and 17 subgroups). Notably, the TMI also demonstrated the highest stability in cutoff values (SD = 0.49, range = 1.89) and superior diagnostic performance (accuracy = 0.84, precision = 0.70, recall = 0.83, F score = 0.75).

Conclusions: Our findings indicate that the TMI is the best anthropometric indices for screening for obesity in children and adolescents on the Tibetan Plateau, with a wide range of applicability to population subgroups and a stable optimal cutoff value.