Measuring the pain impact in adults with a chronic pain condition: adaptation and validation of the Pain Impact Questionnaire (PIQ-6) to the Portuguese culture.

OBJECTIVE: The aim of this study was to validate the Pain Impact Questionnaire (PIQ-6) for Portuguese adults with a chronic pain condition.
DESIGN: The Portuguese version was developed through forward-backward translations and a cognitive debriefing with chronic pain patients. A subsequent sample of patients was selected to test the validity and the obtained Portuguese measure. PATIENTS AND
SETTING: Patients are comprised of a sample of 104 physical therapy patients with chronic pain from four outpatient clinics. OUTCOMES MEASURES: Reliability and validity were tested by administering the PIQ-6, the Medical Outcomes Study-12-Item Short Form (SF-12) questionnaire, a numerical rating pain scale, and a form to collect some of the characteristics of the patients.
RESULTS: After obtaining the semantic and content equivalence, the Portuguese version of PIQ-6 showed good levels of reproducibility (intraclass correlation coefficient between 0.82 and 0.94) and good levels of internal consistency, with Cronbach's alpha of 0.92. The factor analysis confirmed the unidimensionality of the measure (initial eigen-value = 4.29, 71.6%). Construct validity was supported by the correlations obtained with a numerical rating pain scale (rho = 0.705), SF-12 subscales (r = -0.723 and -0.656), and the age of the patients (r = 0.274).
CONCLUSION: The PIQ-6 proved to be equivalent in both cultures (American/Portuguese), and is useful, reliable, and valid for use in Portugal. Wiley Periodicals, Inc.