Validity and Reliability of Thai Version of the Missoula-Vitas Quality-of-Life Index

Abstract

              Quality of life is an important outcome measure of palliative care among people who are terminally ill; however, there are no specific instruments to measure this outcome in Thailand. This study examined the validity and reliability of Thai version of the Missoula-Vitas Quality-of-Life Index. Four steps were used: forward-backward translation; content validity testing by expert committee confirmation; construct validity testing by the convergent, known-groups technique and exploratory factor analysis; and internal consistency reliability testing. One hundred and eighty Thais with advanced cancer receiving palliative care at 5 healthcare settings participated in the convergent, exploratory factor analysis and reliability testing, and 126 were a part of the 180 participants in the known-groups technique. The sample size was determined via estimation of the population proportion from each of the selected study sites. The Thai version of the Index has acceptable content validity and known group technique can differentiate quality of life total scores, functional and interpersonal dimensions. Factor analysis yielded seven factors accounting for 60.88% of variance and five domains of the original Index accounting for 49.9% of variance. An examination of the factor loadings did not support the theoretical structure of the instrument and the internal consistency reliability in each dimension was rather low. The instrument may not have suitable psychometric properties but has some clinical utility for assessing the overall quality of life. Therefore we recommend that another instrument for people with advanced cancer within the Thai cultural context be developed and tested.