Chest
Volume 139, Issue 4, April 2011, Pages 878-886
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Original Research
Pulmonary Function Testing
The Nonspecific Pulmonary Function Test: Longitudinal Follow-up and Outcomes

https://doi.org/10.1378/chest.10-0804Get rights and content

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.

Section snippets

Materials and Methods

The study was carried out at the Mayo Clinic in Rochester, Minnesota. The study was approved by the local institutional review board and only included subjects who had provided research authorization. There were no commercial interests involved with the study. A computerized database of all PF tests performed from the years 1990 to 2005 at the three Mayo Clinic facilities in the United States (Rochester, Minnesota; Jacksonville, Florida; and Scottsdale, Arizona) served as the reference database.

Results

From 1990 to 2005, we identified 1,284 subjects who had an NS pattern and at least one follow-up PF test 6 months or more after the initial NS test. Baseline PF, demographic, and smoking data are described (Tables 2, 3). A cohort of 33,132 normal PF tests from the same time period was used for purposes of comparison (Table 2). Subjects were also divided into four groups each for age, BMI, SVC − FVC (mL), and Sraw as described in the “Materials and Methods” section.

The rate of change of FEV1,

Discussion

This article provides, for the first time, to our knowledge, longitudinal follow-up and outcomes for the NS PF pattern. Our data clearly show that the NS pattern remains stable in a majority of subjects over a median follow-up period of 3 years with about two-thirds of our study subjects continuing to show the NS pattern at the end of the follow-up period (Fig 1). The NS pattern remains the dominant pattern (61%) even in those patients followed for > 5 years after their initial NS PF test (

Acknowledgments

Author contributions: Dr Iyer: contributed to study design, planning, and writing the article.

Mr Schroeder: contributed to statistical analysis.

Mr Parker: contributed to data retrieval and technical support.

Dr Hyatt: contributed to study design, planning, and writing the article.

Dr Scanlon: contributed to study design, planning, and writing the article.

Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any

References (16)

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