Patient utilities in chronic musculoskeletal pain: how useful is the standard gamble method? Fibromyalgia research

The main goal of current pain management approaches is to

increase the patients’ quality of life by improving pain

coping skills and by reducing the levels of disability in

daily life, often despite persistent pain. Direct measurement

of quality of life is of crucial importance in economic

evaluation research, in which not only is the estimation of

financial costs and benefits included, but so is the

evaluation of costs and benefits in terms of changes in health


The purpose of this study is to compare the

psychometric qualities of two instruments for assessing

patients’ utilities, the rating scale (RS) and the standard

gamble (SG). Such instruments are designed for their

application in economic evaluation research, but have seldomly

been used in chronic pain trials. Both methods provide a

single measure between 0 and 1. The relationship between these

utility measures and descriptive and domain-specific quality

of life measures was examined in 133 fibromyalgia patients and

148 patients with chronic non-specific low back pain. Mean

utility score at baseline was 0.43 with the RS and 0.78 for

the SG. The correlation between both methods was found to be

poor (r = 0.21). Both measures appeared to be fairly stable in

a 2-week test-retest period (intra class correlation

coefficient (ICC) = 0.74 and 0.77).

Scores on the description

of patient’s own health on six domains, global assessment of

change and domain specific measures correlated moderately with

the RS scores and low with the SG. Multiple regression

analyses demonstrated that 32% of the variance in RS values

and only 13% of the variance in SG utilities could be

explained by domain-specific measures. These results suggest

an acceptable construct validity for the RS but insufficient

construct validity for the SG. Valuations of ones own health

appear only partially to be related to the assessment of the

pain-specific measures and measures of distress. It can be

concluded that the RS and domain-specific measures assess

partly different, but nevertheless complementary aspects of

health- related quality of life. It is therefore recommended

to include in economic evaluation studies both domain-specific

measures and valuation measures. Finally, in chronic

musculoskeletal pain patients, RS scores were found to be more

responsive in detecting significant changes in preferences

than SG scores. For use in patients with chronic

musculoskeletal pain, the RS is preferred to the SG for

establishing accurate decisions about the impact of new

interventions on their health outcomes.

Goossens ME, Vlaeyen JW, Rutten-van Molken MP, van der Linden SM

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