Use of the palliative outcome scale in Argentina: a cross-cultural adaptation and validation study

Although measuring outcomes is essential to ensuring palliative care effectiveness, there is an absence of properly validated measures in many countries. We undertook a cross-cultural adaptation and validation of the Palliative Outcome Scale (POS) into a Spanish (Argentina) language and cultural context. The methodology used a sequence of phases: 1) verification of conceptual equivalence (literature review, professional interviews, and patient focus groups); 2) multiple translations; 3) committee review; and 4) field testing. Psychometric analysis entailed evaluation of quantitative content validity, construct validity, staff and patients' ratings comparison, internal consistency, test-retest reliability, and responsiveness to change. Conceptual equivalence was achieved. Multiple changes were introduced after the translations and field testing in 65 patients and 20 professionals. Content validity was high for all but one item. Construct validity against a validated quality-of-life measure (European Organization for Research and Treatment of Cancer Quality of Life C-30) was confirmed (rho=0.74, P<0.0005). There was acceptable agreement between staff and patients (Cohen's weighted kappa >0.3) for 5/10, 8/10, and 6/9 items at each of three time-point evaluations and good correlation for all but one item (Spearman coefficient >0.7). Internal consistency was acceptable (Cronbach's alpha=0.68-0.69 and 0.66-0.73) for patient and staff ratings, respectively, and test-retest reliability showed very high agreement for every item (>0.80). The Argentine POS showed adequate responsiveness to change, although significant difference was reached for only 3 out of 10 items for patients and staff, respectively. Completion of the POS did not take more than 12 and 6 minutes for patients and staff, respectively. This study indicates that the Argentine POS is a valid and reliable measure of palliative care outcomes with advanced cancer patients.