Health-related quality of life -: testing the reliability of the MSQOL-54 instrument among MS patients

The purpose of the study was to assess the reliability of the specific multiple sclerosis quality of life (MSQOL-54) instrument, which contains 54 items measuring quality of life, among Finnish multiple sclerosis (MS) patients. Nursing professionals evaluated the clarity and comprehensibility of the translated instrument, after which it was pilot-tested. The data were collected through a questionnaire survey in the spring 2004. Persons diagnosed with MS in 1999-2001 filled in the questionnaire (n = 100). The response percentage was 81%. The structural validity of the MSQOL-54 instrument was evaluated with factor analysis and the generic 15D quality of life instrument. The internal consistency of the instrument was measured with Cronbach's alpha, correlations and item analysis. According to the results, the structural validity of MSQOL-54 was good, and factor analysis yielded a clear-cut factorial model. More than half of the correlations between the comparable items of the 15D and MSQOL-54 instruments were moderate or better. The internal consistency of MSQOL-54 can hence be considered quite good: Cronbach's alpha coefficients calculated for the factors and their items ranged within 0.33-0.89. The alpha coefficient calculated for the whole instrument was 0.84. The internal consistency of MSQOL-54 was further confirmed by the results of an item analysis, which showed the correlation coefficients between the items of the different dimensions to be good (0.31-0.81). On the basis of the test results, the MSQOL-54 instrument is fairly reliable and suitable for assessing the health-related quality of life of MS patients. The reliability of MSQOL-54 should be evaluated further by a longitudinal study design in the future.