Performance of the Dutch SF-36 version 2 as a measure of health-related quality of life in patients with rheumatoid arthritis

Table 1 Scaling assumptions of the SF-36v2 (N = 1884)

		Range of correlations		Item scaling tests
Scales	k^a	Item internal consistency^b	Item discriminant validity^c	Item internal consistency^d	Item discriminant validity^e
PF	10	0.58 to 0.79	0.24 to 0.64	10/10 (100%)	69/70 (98.6%)
RP	4	0.84 to 0.90	0.43 to 0.68	4/4 (100%)	28/28 (100%)
BP	2	0.81	0.36 to 0.70	2/2 (100%)	14/14 (100%)
GH	5	0.48 to 0.68	0.26 to 0.60	5/5 (100%)	31/35 (88.6%)
VT	4	0.36 to 0.69	0.22 to 0.62	3/4 (75%)	27/28 (96.4%)
SF	2	0.70	0.50 to 0.66	2/2 (100%)	13/14 (92.9%)
RE	3	0.86 to 0.91	0.39 to 0.64	3/3 (100%)	21/21 (100%)
MH	5	0.64 to 0.76	0.25 to 0.62	5/5 (100%)	35/35 (100%)

^aNumber of items; ^bPearson correlations between items and hypothesized scales corrected for overlap (correlation with the sum of the other items in the same scale); ^cPearson correlations between items and other scales; ^dNumber (%) of items out of k with correlation ≥ 0.40; ^eNumber (%) of items out of 7xk where the difference between the corrected correlation of the item with its own scale and correlation with the other scales ≥ 2SE (= 0.046). PF = Physical Functioning; RP, Role-physical; BP, Bodily pain; GH, General health; VT, Vitality; SF, Social functioning; RE, Role-emotional; MH, Mental health; HT, Health transition.

ISSN: 1477-7525