Adaptation and validation of the Spanish version of the patient-oriented prostate utility scale (PORPUS)

Abstract

Objective: the Patient-Oriented Prostate Utility Scale (PORPUS) is a combined profile and utility-based quality of life measure for prostate cancer patients. Our objectives were to adapt the PORPUS into Spanish and to assess its acceptability, reliability, and validity. Methods: the PORPUS was adapted into Spanish using forward and back translations and cognitive debriefing. PORPUS was administered jointly with the SF-36 and the Expanded Prostate Index Composite (EPIC) to 480 Spanish prostate cancer patients treated with radical prostatectomy or radiotherapy. The Spanish PORPUS scores' distribution and reliability were examined and compared with the original instrument. To evaluate construct validity, relationships were assessed between PORPUS and other instruments (testing hypotheses of the original PORPUS study), and among known groups defined by side effect severity. Results: reliability coefficient was 0.76 (similar to the original PORPUS' 0.81). Spanish PORPUS items presented correlations ranging 0.57-0.88 with the corresponding EPIC domains, as in the original PORPUS study (0.60-0.83). Both PORPUS-P and PORPUS-U showed significant differences and large effect sizes (0.94-1.90) when comparing severe versus no problem groups on urinary, bowel, sexual and hormonal side effects defined by EPIC. Conclusions: a conceptually equivalent Spanish version was obtained, with high reliability and good construct validity, similar to the original Canadian PORPUS version. It can therefore be used to measure health-related quality of life and utilities in Spanish prostate cancer patients.