Modelling the relationship between the WOMAC osteoarthritis index and EQ-5D

Table 2 Parameter estimates from the 5 class mixture model

		Class 1			Class 2			Class 3			Class 4			Class 5
	Parameter	*p-value*			*p-value*			*p-value*			*p-value*			*p-value*
Within class	Pain/10	0.0166	0.260		−0.2357	0.000	***	0.1475	0.000	***	0.001	0.285		0.0116	0.600
	Stiffness/10	0.0118	0.583		−0.0287	0.760		−0.0182	0.662		−0.0029	0.057	*	0.0037	0.914
	Function/10	−0.0356	0.000	***	−0.0274	0.103		−0.07	0.000	***	−0.0003	0.087	*	−0.0403	0.000	***
	Variance	0.0024	0.000	***	0.0406	0.000	***	0.0047	0.001	***	0	0.000	***	0.0058	0.002	***
Random effects terms	Intercept	0.7636	0.000	***	0.3762	0.000	***	0.9662	0.000	***	0.555	0.000	***	0.2118	0.000	***
	Age¹	0.005	0.000	***
	Male	0.0083	0.000	***
	Variance	0.0016	0.000	***
Class probabilities	Intercept	8.8821	0.000	***	7.0881	0.000	***	11.4076	0.000	***	5.1497	0.0004	***
	Pain/10	−5.1772	0.006	***	−7.9363	0.000	***	−13.4885	0.000	***	−6.4654	0.0006	***
	Stiffness/10	−1.0227	0.625		−6.1566	0.004	***	−0.7275	0.751		−1.0918	0.6023
	Function/10	−1.3706	0.026	**	−0.9434	0.162		−2.0612	0.002	***	0.37	0.5729
	(Pain/10)²	1.2266	0.114		2.3464	0.001	***	4.5149	0.000	***	1.4951	0.0568	*
	(Stiffness/10)²	−1.158	0.604		3.7049	0.156		−1.483	0.570		−1.3521	0.5465
	(Function/10)²	0.0797	0.286		0.1946	0.008	***	0.2545	0.001	***	−0.0626	0.4179
EQ-5D estimates by class	Mean	0.678			0.124			0.881			0.557			0.106
	Median	0.679			0.129			0.865			0.557			0.107
	Min	0.307			−0.594			0.335			0.382			−0.377
	Max	1			1			1			0.748			0.598
	Proportion of ones	0.004			0.001			0.431			0.000			0.000
	Prob of class membership	0.333			0.109			0.240			0.146			0.172

ISSN: 1477-7525