Determination of the minimal clinically significant difference on a patient visual analog satisfaction scale

Abstract

Objective: To determine the minimal clinically significant difference (MCSD) on a visual analog patient satisfaction scale.

Methods: The authors prospectively collected patient satisfaction evaluations during a clinical trial assessing the effect of introducing personal television sets on overall patient satisfaction from their ED encounters. Patient satisfaction was assessed with 2 scales: a 100-mm visual analog scale (VAS) (0 = least satisfied, 100 = most satisfied) and a 7-point categorical scale ("terrible," "mostly dissatisfied," "mixed," "partially satisfied," "mostly satisfied," "pleased," and "delighted"). The differences between the mean VAS scores of "delighted" and "pleased" patients, and between "pleased" and "mostly satisfied" patients were used to determine the MCSD on the VAS. Reliability of each of the scales was determined.

Results: 181 patients were evaluated. Mean age was 41 years; 59% were female. On a subset of 19 patients, the VAS yielded an interobserver correlation of 0.93. The kappa measurement of agreement on the categorical scale was 0.77. The mean difference between "delighted" and "pleased" patient VAS satisfaction scores was 6.8 mm (95% CI, 1.3-12.3 mm). The mean difference between "pleased" and "mostly satisfied" patient VAS satisfaction scores was 10.7 mm (95% CI, 5.5-15.8 mm).

Conclusion: The MCSD in patient satisfaction scores measured with a 100-mm VAS was approximately 7-11 mm. Future studies evaluating differences in patient satisfaction should be designed to detect this difference.