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

Chest. 2011 Apr;139(4):878-886. doi: 10.1378/chest.10-0804. Epub 2010 Aug 19.


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.

Publication types

  • Comparative Study

MeSH terms

  • Disease Progression
  • Female
  • Follow-Up Studies
  • Forced Expiratory Flow Rates / physiology*
  • Humans
  • Male
  • Middle Aged
  • Prognosis
  • Pulmonary Fibrosis / diagnosis
  • Pulmonary Fibrosis / physiopathology*
  • Respiratory Function Tests / methods*
  • Retrospective Studies
  • Severity of Illness Index
  • Time Factors
  • Total Lung Capacity / physiology*