Physical functional capacity in idiopathic pulmonary fibrosis: performance characteristics of the continuous-scale physical function performance test

Abstract

Background: Physical functional capacity is impaired in idiopathic pulmonary fibrosis (IPF). There is no tool to measure this key clinical outcome. The continuous-scale physical function performance (CS-PFP) test is one that assesses activities of daily living, but it has never been used in IPF. Methods: We determined internal consistency of the CS-PFP. We used correlations to assess the strength of association between CS-PFP scores and various parameters of IPF severity, and compared the CS-PFP scores between patients with IPF and published values from a healthy control group. Results: Sixteen subjects completed the test and retest. Test-retest reliability (0.84, p = 0.003) and internal consistency (Cronbach’s α = 0.91) were excellent. Subjects with IPF had significantly worse CS-PFP scores than controls (46.0 ± 11.1 vs 58.7 ± 12.5, p = 0.001). In IPF, the CS-PFP scores correlated moderately to very strongly with several disease severity variables. Conclusion: The CS-PFP is a reliable and valid tool in IPF.

Keywords:

• interstitial lung disease
• patient-oriented outcome
• physical functional capacity
• idiopathic pulmonary fibrosis
• validity

Financial & competing interests disclosure

This project was funded by a microgrant to AL Olson from National Jewish Health. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Idiopathic pulmonary fibrosis (IPF) is the most common of the idiopathic interstitial pneumonias and has the worst prognosis.

• IPF substantially impairs quality of life, primarily through dyspnea-induced limitations in physical functioning.

• While impairment in physical functional capacity – or the ability to perform basic activities and participate in life situations – is known to occur in IPF patients, consensus on how to assess physical functional capacity is lacking.

• The continuous-scale physical function performance (CS-PFP) test is a test of physical functional capacity that directly assesses activities of daily living, and has been used in a number of disease states and in a healthy aging population.

• In this study, we sought to determine the test-retest reliability and internal consistency of the CS-PFP in a cohort of IPF subjects with a range of disease severity.

• We found that the CS-PFP test-retest intraclass correlation coefficient was 0.84 (p = 0.003) indicating excellent test-retest reliability.

• We found that the CS-PFPF had a Cronbach’s α of 0.91 indicating excellent internal consistency.

• CS-PFP scores showed that compared with a healthy, age-matched cohort, IPF patients have greatly impaired physical functional capacity and are at significant risk for losing their ability to live independently.

• Given these novel findings, we believe further study of the CS-PFP as a tool to assess the functional status in IPF patients is warranted.

Notes