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Relative versus absolute change in forced vital capacity in idiopathic pulmonary fibrosis

Relative versus absolute change in forced vital capacity in idiopathic pulmonary fibrosis
Relative versus absolute change in forced vital capacity in idiopathic pulmonary fibrosis
BACKGROUND: Decline in forced vital capacity (FVC) over time reliably predicts mortality in patients with idiopathic pulmonary fibrosis. The use of this measure in clinical practice is recommended by current evidence-based guidelines. It is unknown if the method of calculating decline in FVC (relative vs. absolute change) impacts its frequency or its ability to predict mortality.

METHODS: Patients with idiopathic pulmonary fibrosis from two prospective cohorts were included if they had a baseline and 12-month follow-up FVC. A ?10% decline in FVC from baseline was calculated in two ways: a relative decline of 10% (e.g., from 60% predicted to 54% predicted) and an absolute decline of 10% (e.g., from 60% predicted to 50% predicted). The frequency of a ?10% decline in FVC and its ability to predict 2-year transplant-free survival were compared between these two methods. Declines in FVC of ?5% and ?15% were similarly compared. Analyses were performed unadjusted and adjusted for age, gender, use of oxygen, baseline FVC and baseline diffusion capacity for carbon monoxide.

RESULTS: The frequency of any given FVC decline was significantly greater using the relative change in FVC method. For ?10% decline, both methods predicted 2-year transplant-free survival with similar accuracy, and remained significant predictors after adjusting for baseline characteristics. The absolute change method appeared more predictive for ?5% decline.

CONCLUSIONS: Using the relative change in FVC maximises the chance of identifying a ?10% decline in FVC without sacrificing prognostic accuracy. This may not hold true for ?5% decline in FVC. These findings have important implications for clinical practice and the design of clinical trials.

0040-6376
407-411
Richeldi, L.
47177d9c-731a-49a1-9cc6-4ac8f6bbbf26
Ryerson, C.J.
207ff7c1-47ea-492c-bbc1-6f0489603be3
Lee, J.S.
0612c59b-8bf2-4df5-967a-9ccea69ebf79
Wolters, P.J.
1d6be46d-484d-40ea-ba68-d21f57f4fab0
Koth, L.L.
a4cfdcb8-ee1e-4409-84a4-c8f916ed8c47
Ley, B.
e82a9484-a953-4612-8865-86ebcd8b9466
Elicker, B.M.
2e559c60-197f-47cf-99f7-40d61c4943e0
Jones, K.D.
7fa34bec-5a3f-4522-8665-e280a7a98f6e
King, T.E. Jr
2e34ce6c-db67-4b52-a9a4-d36b49364771
Ryu, JH
012bda37-9ab5-4b6d-a3b7-81bf142a62f1
Collard, H.R.
2947b079-b836-47a6-8319-24ac7d614ea8
Richeldi, L.
47177d9c-731a-49a1-9cc6-4ac8f6bbbf26
Ryerson, C.J.
207ff7c1-47ea-492c-bbc1-6f0489603be3
Lee, J.S.
0612c59b-8bf2-4df5-967a-9ccea69ebf79
Wolters, P.J.
1d6be46d-484d-40ea-ba68-d21f57f4fab0
Koth, L.L.
a4cfdcb8-ee1e-4409-84a4-c8f916ed8c47
Ley, B.
e82a9484-a953-4612-8865-86ebcd8b9466
Elicker, B.M.
2e559c60-197f-47cf-99f7-40d61c4943e0
Jones, K.D.
7fa34bec-5a3f-4522-8665-e280a7a98f6e
King, T.E. Jr
2e34ce6c-db67-4b52-a9a4-d36b49364771
Ryu, JH
012bda37-9ab5-4b6d-a3b7-81bf142a62f1
Collard, H.R.
2947b079-b836-47a6-8319-24ac7d614ea8

Richeldi, L., Ryerson, C.J., Lee, J.S., Wolters, P.J., Koth, L.L., Ley, B., Elicker, B.M., Jones, K.D., King, T.E. Jr, Ryu, JH and Collard, H.R. (2012) Relative versus absolute change in forced vital capacity in idiopathic pulmonary fibrosis. Thorax, 67 (5), 407-411. (doi:10.1136/thoraxjnl-2011-201184). (PMID:22426899)

Record type: Article

Abstract

BACKGROUND: Decline in forced vital capacity (FVC) over time reliably predicts mortality in patients with idiopathic pulmonary fibrosis. The use of this measure in clinical practice is recommended by current evidence-based guidelines. It is unknown if the method of calculating decline in FVC (relative vs. absolute change) impacts its frequency or its ability to predict mortality.

METHODS: Patients with idiopathic pulmonary fibrosis from two prospective cohorts were included if they had a baseline and 12-month follow-up FVC. A ?10% decline in FVC from baseline was calculated in two ways: a relative decline of 10% (e.g., from 60% predicted to 54% predicted) and an absolute decline of 10% (e.g., from 60% predicted to 50% predicted). The frequency of a ?10% decline in FVC and its ability to predict 2-year transplant-free survival were compared between these two methods. Declines in FVC of ?5% and ?15% were similarly compared. Analyses were performed unadjusted and adjusted for age, gender, use of oxygen, baseline FVC and baseline diffusion capacity for carbon monoxide.

RESULTS: The frequency of any given FVC decline was significantly greater using the relative change in FVC method. For ?10% decline, both methods predicted 2-year transplant-free survival with similar accuracy, and remained significant predictors after adjusting for baseline characteristics. The absolute change method appeared more predictive for ?5% decline.

CONCLUSIONS: Using the relative change in FVC maximises the chance of identifying a ?10% decline in FVC without sacrificing prognostic accuracy. This may not hold true for ?5% decline in FVC. These findings have important implications for clinical practice and the design of clinical trials.

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Published date: 17 March 2012
Organisations: Faculty of Medicine

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Local EPrints ID: 353516
URI: http://eprints.soton.ac.uk/id/eprint/353516
ISSN: 0040-6376
PURE UUID: 779fec6b-402e-4330-9209-632400021b43

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Date deposited: 10 Jun 2013 12:53
Last modified: 16 Jul 2019 21:31

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Contributors

Author: L. Richeldi
Author: C.J. Ryerson
Author: J.S. Lee
Author: P.J. Wolters
Author: L.L. Koth
Author: B. Ley
Author: B.M. Elicker
Author: K.D. Jones
Author: T.E. Jr King
Author: JH Ryu
Author: H.R. Collard

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