Measurement of global functional performance in patients with rheumatoid arthritis using rheumatology function tests

Table 2 Comparative fit of multivariate models containing different rheumatology function tests.

	Rheumatology function test scale included as independent variable in multivariate model^a
	Primary RFT scale
Dependent variable	Grip strength	Walking velocity	Button speed	Derived global physical function^b
Currently working	-4430	-4455	-4438	-4462***
Currently disabled	-4260	-4283	-4283	-4298***
Death within 6 years	-4673	-4677	-4679	-4689***
Pain	-159	-171	-156	-170**
Tender-joint count	828	894	907	824**
Swollen-joint count	-69	-9	7	-37**
Deformed-joint count	556	620	571	535***
MHAQ scale	-3788	-3880	-3816	-4002***
SF36PF scale	-253	-695	-549	-763***
Steinbrocker functional class	-3564	-3707	-3633	-3787***
Latent disability scale	-3277	-3481	-3334	-3635***

Values shown are Bayesian information criteria. ^aModel's form was y = age + sex + physical disability scale, where y = dependent variable. For current working, currently disabled and death by 6 years, the model was logistic; for other variables, model was ordinary least squares. ^bExtracted from a principal component factor analysis of grip strength, walking velocity, and button speed (see Fig. 1). **Strong or very strong support in favor of model that includes the latent variable, over two of the primary tests. ***Strong or very strong support in favor of model that includes the latent variable, over three of the primary tests. MHAQ, Modified Health Assessment Questionnaire; RFT, rheumatology function test; SF36PF, short-form 36 physical function scale.

ISSN: 1478-6362