Table 4.
Validity of BMI cut-off for detecting obesity among Ethiopian adults as compared to obesity based on the body fat percentage determined by the air displacement plethysmography (ADP)
| Sex | Cut-off values | TP (a) | FP (b) | FN (c) | TN (d) | Total | Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) | Kappa | Agreement | P |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Males | BMI ≥ 30 kg/m2 | 8 | 1 | 144 | 154 | 307 | 5.3 | 99.4 | 88.9 | 51.7 | 0.047 | Slight | 0.0160 |
| BMI > 22.2 kg/m2a | 133 | 19 | 19 | 136 | 307 | 87.5 | 87.7 | 87.5 | 87.7 | 0.752 | Substantial | < 0.0001 | |
| Females | BMI ≥ 30 kg/m2 | 75 | 0 | 185 | 137 | 397 | 46.9 | 100.0 | 100.0 | 42.5 | 0.219 | Fair | < 0.0001 |
| BMI > 24.5 kg/m2a | 208 | 6 | 52 | 131 | 397 | 80.0 | 95.6 | 97.2 | 71.6 | 0.701 | Substantial | < 0.0001 |
Sensitivity = a/a + c, specificity = d/b + d, positive predictive value (PPV) = a/a + b, negative predictive value (NPV) = d/c + d. Kappa agreement (0 = no/poor), (0.01–0.20 = slight), (0.21–0.40 = fair), (0.41–0.60 = moderate), (0.61–0.80 = substantial), and (0.81–1.00 = almost perfect) (William et al., 2011). ADP measured body fat percentage > 25 for males and > 35 for females was used as a gold standard [20]. BMI cut-off for obesity ≥ 30 kg/m2 is the WHO cut-off [20]
ADP air displacement plethysmography
aEthiopian sex-specific cut-off for BMI for defining obesity based on the local data