Diagnostic performance of skinfold method to identify obesity as measured by air displacement plethysmography in cardiac rehabilitation

Purpose: To assess the diagnostic performance of the skinfold (SKF) method to detect obesity in patients enrolled in an outpatient cardiac rehabilitation (CR) program. Methods: This study involves outpatients attending a phase II CR program who underwent air displacement plethysmography (ADP) to assess body composition. We measured body fat percentage (BF%), using a 3-site SKF method calculated through the Jackson-Pollock equation utilizing a Harpenden caliper. Air displacement plethysmography calculated BF% using a bicompartmental model, deriving the body composition after the direct calculation of body density (BD), using the Siri equation [(BF% = 495/BD) - 450]. We calculated the diagnostic performance of SKF to detect obesity, utilizing a BF% cutoff of ≥35% for women and ≥25% for men determined by SKF and ADP to define obesity. Results: Our sample (n = 310) was 80% men, 60.2 ± 11 years of age, had a mean weight of 89.88 ± 17.96 kg, height 173.38 ± 8.68 cm, body mass index (BMI) 29.78 ± 5.01 kg/m, waist circumference 100.55 ± 14.38 cm, and waist-to-hip ratio of 0.96 ± 0.09. The evaluation of the diagnostic performance of SKF to detect obesity showed a sensitivity of 57%, specificity of 93%, a positive predictive value of 97%, and a negative predictive value of 33%. These values were not different from the diagnostic performance of BMI to detect obesity as defined by BF%. SKF and BMI misclassified 43% and 49% of obese patients as nonobese, respectively. Conclusion: Our findings underscore the limitation of using SKF to assess body fatness in the CR setting.