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Stuge B.1, Jenssen H.K.2, Grotle M.3
1Oslo University Hospital, Division of Orthopaedic Surgery, Oslo, Norway, 2Oslo University Hospital, Oslo, Norway, 3Oslo and Akershus University College of Applied Sciences, Oslo, Norway
Background: The Pelvic Girdle Questionnaire (PGQ) is a condition-specific measure developed for women with pelvic girdle pain (PGP). The PGQ includes items relating to activity/participation and bodily symptoms, has acceptably high reliability and validity, satisfactory discriminative validity, is simple to administer and feasible for use in research and in clinical practice.
Purpose: To examine the responsiveness of the PGQ in women with PGP and/or low back pain (LBP), to determine the minimal important change (MIC) and to compare the responsiveness and the MIC of the PGQ with other commonly used outcome measures.
Methods: This prospective cohort study consists of a sample of 801 pregnant who responded to a booklet of questionnaires in their last trimester and within three months postpartum. Together with sociodemographic variables commonly used patient reported outcomes were included. The Self-rated Global Perceived Effect (GPE) was used as the anchor (gold standard) with the following question:
How is your PGP and/or LBP now compared towards the end of pregnancy?
Classification of improved or not improved was based on seven response categories. Responsiveness analyses followed recommendations from The COSMIN (COnsensus-based Standards for the selection of health Measurement INstruments) checklist. The MIC was calculated using the external anchor for change of pain and the receiver operator characteristic (ROC) method. A-priori hypotheses concerning change in the outcome measures were based on expected Effect sizes (ES) and Standardized Response Means (SRM) for each category of the GPE scale.
Results: The 801 women were mean 31 years old (SD 4), on average pregnant in week 34 (SD 2) and 74 % were first time pregnant. 606 women (76%) reported to have PGP and/or LBP, the remaining 195 reported no PGP and/or LBP. Of the 606 women with pain, 441 (73%) responded to the follow-up questionnaire postpartum. Postpartum, 163 of the responders (37.2%) reported complete recovery, 177 (40.4%) were much improved, 39 (8.9%) were somewhat improved, 7 (1.6%) were the same, 25 (5.7%) reported worsening. The PGQ (both subscales and total score) and evening pain showed the largest ability of correctly discriminating between improved and non-improved participants with an area under the ROC curve above 70%. The SF-8 mental and EQ5D-VAS showed the lowest discriminative ability with an area under the ROC curve below 60%. The MIC values indicate that a change score smaller than 25 for total score and activity subscale and 20 for the symptom subscale should be regarded as not important for the women. The symptom subscale showed the best sensitivity and specificity of the whole sample.
The expectations regarding the hypotheses of ES and SRM were only fulfilled for patients reporting much improvement and completely recovered.
Conclusion(s): Based on the ROC curves the PGQ is an adequately responsive instrument for women with PGP and/or LBP. The PGQ discriminated better than the other disability questionnaires.
Implications: The responsiveness of the PGQ adds to previous literature on reliability and validity. Responsiveness and MIC of an instrument are population- and context specific which should be taken into account before generalizing to other populations.
Funding acknowledgements: We acknowledge the women who participated in the study and the midwifes recruiting the women
Topic: Research methodology & knowledge translation
Ethics approval: The study was approved by the Regional Committee for Medical Research Ethics in Norway 2012/1626(/REK sør-øst B)
All authors, affiliations and abstracts have been published as submitted.
