. Author manuscript; available in PMC: 2015 Apr 1.

Published in final edited form as: J Rheumatol. 2014 Jul 1;41(10):1974–1979. doi: 10.3899/jrheum.140224

Table 3.

Multivariable model for insulin sensitivity index (log) in persons with rheumatoid arthritis.

	Parameter Estimate	Partial R²	P value
*Clinical Model: R²=0.26*
Waist circumference (cm)	−0.01	0.26	0.0005
*Laboratory Model: R²=0.46*
Visceral adiposity area (cm²)	−0.002	0.28	0.005
Thigh inter-muscular adiposity area (cm²)	−0.02	0.12	0.02
IL-6 (log pg/ml)	−0.22	0.07	0.07

Multivariable modeling was performed using linear models with backward stepwise variable selection. For the clinical model, variable inclusion was based on conceptual hypotheses regarding traditional risk factors and disease associated factors impacting S_I and included age, gender, waist circumference, physical activity, disease activity (DAS-28), disease modifying agent use, biologic use, and prednisone use. Based on results from bivariate analyses, for the laboratory model, waist circumference was replaced with visceral adiposity and thigh inter-muscular adiposity, and disease activity was replaced with interleukin (IL)-6; all other variables from the clinical model were included.