The nonspecific pulmonary function test: Longitudinal follow-up and outcomes

Vivek N. Iyer, Darrell R. Schroeder, Kenneth O. Parker, Robert E. Hyatt, Paul D. Scanlon

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


Background: The nonspecific (NS) pulmonary function (PF) pattern refers to a PF test with a normal total lung capacity (TLC), normal FEV1/FVC ratio, and a low FEV1, a low FVC, or both. Currently, no information is available regarding the long-term stability of the NS pattern or variables that predict changes in subjects with an initial NS PF pattern. Methods: From 1990 to 2005 we identified 1,284 subjects with an NS pattern on initial PF testing with one or more follow-up PF tests 6 months or more after the initial NS test result. Lung volumes, diffusing capacity, and spirometry data were analyzed. A multivariate, multinomial logistic regression model was used to study the association between different variables and the final PF pattern. Results: Overall, 3,674 PF tests were performed in 1,284 subjects over a median follow-up period of 3 years. At last follow-up, 818/1,284 (64%) subjects continued to show the NS pattern, whereas 208/1,284 (16%) showed a restrictive pattern, 191/1,284 (15%) an obstructive pattern, 42/1,284 (3%) a normal pattern, and 25/1,284 (2%) a mixed pattern. The multinomial logistic regression analysis showed that increasing values for specific airway resistance and the difference between TLC and alveolar volume were predictors of a change to an obstructive pattern on follow-up. Conclusions: The NS pattern is a distinct and stable PF test pattern with roughly two-thirds of patients continuing to show this pattern on follow-up testing. Current interpretation guidelines erroneously label the NS pattern as representing obstruction and need to be changed to reflect these data.

Original languageEnglish (US)
Pages (from-to)878-886
Number of pages9
Issue number4
StatePublished - Apr 2011

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Critical Care and Intensive Care Medicine
  • Cardiology and Cardiovascular Medicine


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