Background
Childhood cancer survivors (CCS) are at risk for obesity. The purpose of this project was to determine which clinical measures of body composition are most accurate among CCS when compared to dual energy x-ray absorptiometry (DXA).
Methods
We evaluated agreement between body mass index (BMI), skinfolds percent body fat, and waist to height ratio (WHtR), with DXA among 1361 CCS (mean age 32.4±7.7), ≥10 years from diagnosis. We calculated sensitivity and specificity of BMI, skinfolds, and WHtR obesity classifications compared to DXA. Log-binomial regression, stratified by sex, was used to evaluate treatment-related factors for misclassification as non-obese by BMI, skinfolds, and WHtR.
Results
Mean body fat values for skinfolds were 23.3±7.7% (males) and 32.3±8.1% (females), and for DXA, 26.9±7.4% (males) and 38.4±7.7% (females). Pearson correlations between skinfolds and DXA were high: R=0.83 males, R=0.84 female. Skinfolds incorrectly classified 34.5% of obese males and 27.3% of obese females. BMI measures were the least sensitive with false negative rates of 46.4% (males) and 53.1% (females). Males exposed to abdominal/pelvic radiation were at increased risk for misclassification as non-obese by BMI (RR 1.57; 95% CI 1.25–1.95). The percentages classified as obese were highest when using DXA (63.1%, males; 84.8%, females) and lowest when using BMI (35.7%, males; 39.7%, females). Although skinfolds and WHtR underestimated the percentage classified as obese compared to DXA, the differences were not as large.
Conclusion
Findings suggest that skinfolds and WHtR are better than BMI for obesity classification in CCS. Clinicians should be aware of the high risk of misclassifying obese CCS as non-obese.