A simple visual analog scale for pain is as responsive as the WOMAC, the SF-36, and the EQ-5D in measuring outcomes of revision hip arthroplasty

Figures & data

Scale scores before and 2 years after revision hip arthroplasty in 45 patients

Scale	Preoperatively ^a	Postoperatively ^a	Score change ^a, ^b	Effect size (95% CI) ^c
WOMAC
Pain	43 (23)	81 (20)	38 (32)	1.7 (1.2–2.1)
Physical function	35 (18)	64 (22)	29 (26)	1.6 (1.1–2.1)
Stiffness	38 (21)	72 (21)	35 (34)	1.6 (1.2–2.1)
SF-36
Bodily pain	31 (22)	61 (27)	29 (35)	1.4 (0.91–1.8)
Physical functioning	33 (22)	52 (25)	19 (29)	0.8 (0.40–1.3)
Physical Role	13 (27)	38 (44)	26 (52)	0.9 (0.49–1.4)
Vitality	43 (23)	57 (26)	14 (20)	0.6 (0.62–1.1)
EQ-5D
Index	0.35 (0.31)	0.74 (0.17)	0.38 (0.32)	1.2 (0.78–1.7)
VAS	44 (25)	73 (19)	29 (29)	1.1 (0.67–1.6)
VAS pain	63 (20)	20 (20)	–43 (26) ^d	–2.1 (–2.7 to –1.6) ^d

^a Values are mean (SD) for preoperative and postoperative scores and score changes. Score ranges: WOMAC and SF-36 from 0 (worst) to 100 (best); EQ-5D index from –0.594 (worst) to 1.0 (best), and VAS pain from 0 (best) to 100 (worst).

^b p < 0.001 for all comparisons, except for Physical role (p = 0.002).

^c Effect size = mean score change divided by SD of baseline score.

^d Negative value indicates a decrease (improvement) in VAS pain score.

Bland-Altman plots for pairs of scales measuring the same type of outcome. The differences between score changes (preoperatively to 2 years) for each pair of scales are plotted against the mean of the 2 score changes. The pairs of scales plotted are the WOMAC and SF-36 pain scores (panel A), the WOMAC and VAS pain scores (panel B), and the WOMAC and SF-36 physical function scores (panel C). The mean difference between score changes and the 95% limits of agreement are shown.