The pelvic girdle questionnaire: a condition-specific instrument for assessing activity limitations and symptoms in people with pelvic girdle pain.

BACKGROUND No appropriate measures have been specifically developed for pelvic girdle pain (PGP). There is a need for suitable outcome measures that are reliable and valid for people with PGP for use in research and clinical practice. OBJECTIVE The objective of this study was to develop a condition-specific measure, the Pelvic Girdle Questionnaire (PGQ), for use during pregnancy and postpartum. DESIGN This was a methodology study. METHODS Items were developed from a literature review and information from a focus group of people who consulted physical therapists for PGP. Face validity and content validity were assessed by classifying the items according to the World Health Organization's International Classification of Functioning, Disability and Health. After a pilot study, the PGQ was administered to participants with clinically verified PGP by means of a postal questionnaire in 2 surveys. The first survey included 94 participants (52 pregnant), and the second survey included 87 participants (43 pregnant). Rasch analysis was used for item reduction, and the PGQ was assessed for unidimensionality, item fit, redundancy, and differential item functioning. Test-retest reliability was assessed with a random sample of 42 participants. RESULTS The analysis resulted in a questionnaire consisting of 20 activity items and 5 symptom items on a 4-point response scale. The items in both subscales showed a good fit to the Rasch model, with acceptable internal consistency, satisfactory fit residuals, and no disordered threshold. Test-retest reliability showed high intraclass correlation coefficient estimates: .93 (95% confidence interval=0.86-0.96) for the PGQ activity subscale and .91 (95% confidence interval=0.84-0.95) for the PGQ symptom subscale. Limitations The PGQ should be compared with low back pain questionnaires as part of a concurrent evaluation of measurement properties, including validity and responsiveness to change. CONCLUSIONS The PGQ is the first condition-specific measure developed for people with PGP. The PGQ had acceptably high reliability and validity in people with PGP both during pregnancy and postpartum, it is simple to administer, and it is feasible for use in clinical practice.