RESEARCH ARTICLE
Using Spirometry to Rule Out Restriction in Patients with Concomitant Low Forced Vital Capacity and Obstructive Pattern
Imran Khalid*, 1, Zachary Q Morris2, Tabindeh J Khalid1, 3, Amina Nisar4, Bruno DiGiovine5
Article Information
Identifiers and Pagination:
Year: 2011Volume: 5
First Page: 44
Last Page: 50
Publisher ID: TORMJ-5-44
DOI: 10.2174/1874306401105010044
Article History:
Received Date: 20/12/2010Revision Received Date: 2/5/2011
Acceptance Date: 18/5/2011
Electronic publication date: 23/6/2011
Collection year: 2011
open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.
Abstract
Background:
Different formulas have been proposed to exclude restriction based on spirometry, however none of them have specifically tested the patients whose spirometry show both obstruction and a low forced vital capacity (FVC).
Study Objective:
The study was designed to create an algorithm that would better predict the absence of restriction in such patients.
Design:
Retrospective analysis of prospectively collected data.
Methods:
A cohort of consecutive adults that underwent complete pulmonary function testing from 2002-2004 was analyzed. The data was randomly split into two groups to allow for derivation and then validation of a predictive formula. Patients were randomly assigned into either a “derivation” or “validation” group. In the derivation group, stepwise logistic regression was used to determine a formula and optimal cut-off value for the variable with the best discriminative capacity. The formula was applied subsequently to the validation group to test the results and compared to previously published formula.
Results:
The study group contained 766 patients. We determined that the variable with the highest association with TLC was [(FEV1/FVC) % predicted/FVC % predicted]. A value of ≥1.11 was found to be the maximal cutoff to predict the absence of restriction.
The formula was applied to a validation group (n=397) and performed better than prior published algorithm with a sensitivity, specificity, positive predictive value and negative predictive value of 95%, 44%, 22%, and 98%, respectively.
Conclusion:
Our formula performs superior to the previously published algorithms in patients with concomitant low FVC and obstruction to exclude restriction.
