Objective: To assess the validity of the patient global assessment (PGA) of the method of pain control, a single-item patient-reported outcome measure of a method of pain control for patients experiencing postoperative pain.
Research design and methods: Content validity of the PGA of the method of pain control was assessed using cognitive debriefing interviews. Construct validity was evaluated using data from six clinical trials that compared the efficacy of the fentanyl HCl iontophoretic transdermal system (fentanyl ITS) with morphine intravenous patient-controlled analgesia or placebo fentanyl ITS for acute postoperative pain management.
Main outcome measures: To assess the construct validity of the PGA rating scale, four hypotheses were developed that related positive PGA ratings ('good' or 'excellent') to (1) lower pain intensity scores, (2) higher satisfaction ratings, (3) a greater propensity to select the assigned pain control method in the future, and (4) favorable ratings of ease of use/convenience on the Patient Ease-of-Care Questionnaire. Descriptive statistics were used to evaluate the association of pain intensity and Overall Ease-of-Care scores with PGA ratings. An exact linear-by-linear association test was conducted to evaluate the association of satisfaction ratings and propensity to select the pain control method in the future with PGA ratings.
Results: Results of cognitive debriefing interviews indicated that the PGA incorporates patient perceptions of several aspects of treatment with an analgesic modality, including level of pain, ease of use, and control of administration. PGA ratings were associated in the expected direction with other patient-reported outcomes used in several clinical studies.
Conclusions: Findings suggest that both the content and construct validity of the PGA of the method of pain control in clinical trial settings are supported. However, this conclusion is potentially limited by the use of a narrow range of therapeutic interventions and, in some cases, small sample sizes in the clinical trials used to assess construct validity. The PGA of the method of pain control is an informative and useful measure for assessing pain control provided by different drug delivery systems for patients experiencing postoperative pain.