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
1 King Faisal Specialist Hospital & Research Center, Jeddah, Saudi Arabia
2 Henry Ford Hospital, Detroit, MI, 48202, USA
3 Henry Ford Wyandotte Hospital, MI, 48192, USA
4 Oakwood Hospital and Medical Center, Dearborn, MI, 48124, USA
5 Wayne State University School of Medicine, Detroit, MI, 48201, USA


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© Khalid et al.; Licensee Bentham Open.

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.

* Address correspondence to this author at the King Faisal Specialist Hospital & Research Center, P.O. Box 40047, MBC J102, Jeddah, Saudi Arabia; Tel: 1-734-713-6435; Fax: 1-413-677-8932; E-mails: dr.imrankhalid@yahoo.com, doc_ik@yahoo.com


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.

Keywords: Algorithm, restriction, spirometry, total lung capacity..