Psychometric Properties of the Patient-Reported Outcomes Measure of Pharmaceutical Therapy for Quality of Life (PROMPT-QOL)

Abstract

Objectives: To assess the psychometric properties of a novel instrument for medication management, the Patient-Reported Outcomes Measure of Pharmaceutical Therapy for Quality of Life (PROMPT-QOL), using both conventional psychometrics and Rasch analysis in a large sample.

Methods: This study was conducted with 1156 adult outpatients continuously taking any medicines at least 3 months from three university hospitals in Bangkok, Thailand, between July 2014 and March 2015. The psychometric properties were assessed in five steps: 1) assessment of dimensional structure, 2) item selection, 3) assessment of practicality, 4) assessment of reliability, and 5) assessment of criterion and known-groups validity.

Results: The PROMPT-QOL contained 43 items including nine domains, and their five-point Likert scale functioning worked well. Most items fulfilled the item selection criteria. The PROMPT-QOL took an average administration time of 13.4 ± 5.8 minutes. Only two items had missing data of 0.1% to 0.2%. All domains provided good to excellent test-retest reliability with intraclass correlation coefficients between 0.67 and 0.83. All domains of the PROMPT-QOL yielded high Cronbach's α values between 0.77 and 0.89, greater than an acceptable level of 0.70, except for the Availability and Accessibility domain (0.58). A multiple regression showed that the Medication Effectiveness domain was the strongest predictor of the overall QOL of the PROMPT-QOL, followed by the Therapeutic Relationships, Psychological Impacts, Convenience, and Availability and Accessibility domains (adjusted R² ~ 52%). As expected, patients with higher PROMPT-QOL domain scores were associated with being younger, more educated, having a lower number of medicines, patients' perceptions of better disease control, having no adverse drug reactions, and medicine preference.

Conclusions: The PROMPT-QOL was practical, reliable, and valid for Thai patients.

Keywords: Rasch analysis; Thailand; medicine/pharmaceutical/drug therapy; patient-reported outcomes; psychometrics; quality of life.