Value of body mass index in the diagnosis of obesity according to DEXA in well-controlled RA patients.
BACKGROUND
Rheumatoid arthritis (RA) has an indirect effect on body composition. Body mass index (BMI) is not a valid predictor of body fat in RA patients.


OBJECTIVE
To evaluate the accuracy of BMI in identifying obesity diagnosed according to dual energy X-ray absorptiometry (DXA) in well-controlled RA patients.


METHODS
An observational, cross-sectional, descriptive, analytical study. We used 3 different cutoffs for obesity as determined by DXA: >35% total fat, >40% total fat, and >35% central fat mass (central obesity).


RESULTS
One hundred one patients were included. We found that 35% total fat corresponded to a BMI of 24kg/m2, with a sensitivity of 90% and specificity of 75% (area under the curve [AUC] 0.917); 40% total fat to a BMI of 25kg/m2, with a sensitivity of 86% and specificity of 39% (AUC 0.822); and 35% central fat mass to a BMI of 22kg/m2, with a sensitivity of 97% and specificity of 84% (AUC 0.951).


CONCLUSION
Obesity according to DXA was underdiagnosed when the classic BMI cutoffs were used in well-controlled RA patients.