Psychometric evaluation of the shortened version of the Functional Difficulties Questionnaire to assess thoracic physical function

Katijjahbe MA 1 , Denehy L 2 , Granger CL 2 , Royse A 3 , Royse C 3 , Logie S 4 Show all authors , Sturgess T 5 , Md Ali NA 6 , McManus M 7 , Sandy CE 8 , El-Ansary D 3

Affiliations 

  • 1 Department of Physiotherapy, Hospital Canselor Tuanku Muhriz, Pusat Perubatan University Kebangsaan, Kuala Lumpur, Malaysia
  • 2 Department of Physiotherapy, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC, Australia
  • 3 Department of Health Professions, Faculty of Health, Arts and Design, Swinburne University of Technology, Hawthorn, VIC, Australia
  • 4 Physiotherapy Department, Melbourne Private Hospital, Parkville, VIC, Australia
  • 5 Department of Physiotherapy, Monash Medical Centre, Clayton, VIC, Australia
  • 6 Heart and Lung Centre, Universiti Kebangsaan Malaysia Medical Centre, Kuala Lumpur, Malaysia
  • 7 Canberra Hospital, Garran, ACT, Australia
  • 8 Statistical Consulting Centre, School of Mathematics and Statistics, The University of Melbourne, Parkville, VIC, Australia
Clin Rehabil, 2020 Jan;34(1):132-140.
PMID: 31610700 DOI: 10.1177/0269215519879476

Abstract

OBJECTIVE: The aim of this study was to investigate the psychometric properties of the shortened version of the Functional Difficulties Questionnaire (FDQ).

DESIGN: This is a multisite observational study.

SETTING: The study was conducted in four tertiary care hospitals in Australia.

SUBJECTS: A total of 225 participants, following cardiac surgery, were involved in the study.

INTERVENTION: Participants completed the original 13-item FDQ and other measures of physical function, pain and health-related quality of life.

METHOD: Item reduction was utilized to develop the shortened version. Reliability was evaluated using intraclass correlation coefficients (ICCs), the smallest detectable change and Bland-Altman plots. The validity and responsiveness were evaluated using correlation. Anchor and distribution-based calculation was used to calculate the minimal clinical important difference (MCID).

RESULTS: Item reduction resulted in the creation of a 10-item shortened version of the questionnaire (FDQ-s). Within the cohort of cardiac surgery patient, the mean (SD) for the FDQ-s was 38.7 (19.61) at baseline; 15.5 (14.01) at four weeks and 7.9 (12.01) at three months. Validity: excellent internal consistency (Cronbach's α > 0.90) and fair-to-excellent construct validity (>0.4). Reliability: internal consistency was excellent (Cronbach's α > 0.8). The FDQ-s had excellent test-retest reliability (ICC = 0.89-0.92). Strong responsiveness overtime was demonstrated with large effect sizes (Cohen's d > 1.0). The MCID of the FDQ-s was calculated between 4 and 10 out of 100 (in cm).

CONCLUSION: The FDQ-s demonstrated robust psychometric properties as a measurement tool of physical function of the thoracic region following cardiac surgery.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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