Construct validity and responsiveness of the Colombian version of Skindex-29.

BACKGROUND

In recent years, the need for international, objective, patient-reported outcomes measures has grown as international collaboration has increased. As most quality-of-life scales have been developed in English, there is a growing need to adapt them transculturally to obtain equivalence between the original instrument and the adapted scale.

OBJECTIVES

To assess the construct and convergent-discriminant validity and responsiveness of the Colombian version of Skindex-29.

METHODS

The cross-sectional and longitudinal validity and responsiveness were tested in both healthy and dermatology patients. Construct validity was tested through a confirmatory factor analysis. The convergent-discriminant validity was assessed by examining the Spearman correlation coefficient. Change sensitivity was tested by means of the standardized response mean. The effect size and the minimum detectable change were also assessed.

RESULTS

A total of 265 participants were included; 21·1% were healthy individuals, and 78·9% patients had either inflammatory or noninflammatory skin diseases. Confirmatory factor analysis showed an adequate comparative fit index and Tucker-Lewis index adjustment for the root mean square error of approximation. Convergent validity showed moderate correlations between the emotions, functioning and physical function or physical role domains. Discriminant validity showed low correlations between overall domains for both scales. Sensitivity to change at the first and third month showed effect sizes in global Skindex scores of 0·92 and 0·82, respectively.

CONCLUSIONS

The Colombian version of Skindex-29 is a valid and clinically sensitive instrument, which can be used for clinical practice and for research to measure the impact of skin diseases on the quality of life of dermatology patients.