Minimal Important Difference for Physical Activity and Validity of the International Physical Activity Questionnaire in Interstitial Lung Disease

Seo Am Hur; Sabina A Guler; Nasreen Khalil; Pat G Camp; Jordan A Guenette; Jeffrey J Swigris; Christopher J Ryerson

doi:10.1513/AnnalsATS.201804-265OC

Minimal Important Difference for Physical Activity and Validity of the International Physical Activity Questionnaire in Interstitial Lung Disease

Ann Am Thorac Soc. 2019 Jan;16(1):107-115. doi: 10.1513/AnnalsATS.201804-265OC.

Authors

Seo Am Hur^{1

2}, Sabina A Guler^{1

2}, Nasreen Khalil³, Pat G Camp^{2

4}, Jordan A Guenette^{2

4}, Jeffrey J Swigris⁵, Christopher J Ryerson^{1

2}

Affiliations

¹ 1 Department of Medicine and.
² 2 Centre for Heart Lung Innovation, University of British Columbia and St. Paul's Hospital, Vancouver, British Columbia, Canada.
³ 3 The Lung Centre, Vancouver General Hospital, Vancouver, British Columbia, Canada.
⁴ 4 Department of Physical Therapy, University of British Columbia, Vancouver, British Columbia, Canada; and.
⁵ 5 Interstitial Lung Disease Program in the Autoimmune Lung Centre and the Division of Psychosocial Medicine, National Jewish Health, Denver, Colorado.

PMID: 30211616
DOI: 10.1513/AnnalsATS.201804-265OC

Abstract

Rationale: The optimal method of physical activity measurement has not been determined in patients with fibrotic interstitial lung disease (ILD).

Objectives: To assess the validity, internal consistency, and responsiveness of the International Physical Activity Questionnaire long form (IPAQ-LF) and to estimate the minimal important difference (MID) for moderate to vigorous physical activity (MVPA) in patients with fibrotic ILD.

Methods: This two-center prospective cohort study included a convenience sample of 111 outpatients with fibrotic ILD who wore waist and wrist ActiGraph accelerometers for 7 consecutive days, followed by self-administration of the IPAQ-LF. Both measurements were performed at baseline and 6-month follow-up. Spearman rank correlations were used to evaluate the IPAQ-LF validity in comparison to activity monitor data, lung function, step count, and quality of life. The internal consistency of the IPAQ-LF was determined using Cronbach's α. Self-reported changes in IPAQ-LF parameters were compared among tertiles of change measured by the waist activity monitor to assess the responsiveness of the IPAQ-LF after 6 months. Anchor- and distribution-based methods were used to estimate the MID for MVPA.

Results: Self-reported MVPA minutes, activity-related energy expenditure, sedentary time, and inactive time of the IPAQ-LF generally showed moderate to strong correlations with corresponding waist activity monitor data, step count, lung function, and quality of life. The Cronbach's α of the IPAQ-LF was 0.78. The IPAQ-LF was responsive at detecting increases in weekly MVPA and energy expenditure. The MIDs for MVPA were 8 to 26 and 13 to 58 min/wk using the anchor-based method for waist activity monitor and IPAQ-LF data, respectively. The distribution-based MID estimate for MVPA was 104 to 242 min/wk.

Conclusions: The IPAQ-LF has acceptable validity and internal consistency for measuring daily physical activity in patients with fibrotic ILD. The IPAQ-LF was responsive at detecting increases in physical activity but limited in its ability to detect declines or changes in inactivity. Using an anchor-based approach, the MID for MVPA measured by a waist activity monitor is approximately 26 min/wk.

Keywords: accelerometry; exercise; interstitial lung disease; minimal clinically important difference.

Publication types

Multicenter Study
Research Support, Non-U.S. Gov't
Validation Study

MeSH terms

Accelerometry
Aged
Exercise*
Female
Humans
Linear Models
Lung Diseases, Interstitial*
Male
Middle Aged
Prospective Studies
Quality of Life
Self Report
Surveys and Questionnaires / standards*