Chest
Original ResearchPulmonary PhysiologyInterpreting Lung Function Data Using 80% Predicted and Fixed Thresholds Misclassifies More Than 20% of Patients
Section snippets
Materials and Methods
PFT results were obtained retrospectively from the patient databases of relatively large PFT laboratories from three countries in order to improve the chance that the results can be used to generalize to other populations. Full PFT results from consecutively tested white adults were obtained from the University Hospital Trust (Birmingham, England, United Kingdom) (n = 5,702; men, 51.2%; mean age, 58.3 years; age range, 20-92 years); Saint Louis University Hospital (St Louis, Missouri) (n =
Results
The mean results expressed as standardized residuals10 for FEV1, FVC, TLC, and Dlco for the patients from the three centers are shown in Table 1. The mean results for each index were not significantly different for each laboratory from the other two except for the FEV1 and TLC results for the United States and New Zealand compared with the UK data (P < .005, two-sample t test), which relates to differences in the prediction equations and methodology used for measuring TLC.
When fixed thresholds
Discussion
This study demonstrates that using a percent predicted and fixed thresholds method (GOLD/PP) instead of fifth-percentile LLNs when interpreting lung function results can mean that up to 24% of patients are misclassified with regard to possible lung disease. These errors may vary with the prediction equations applied, sex, ethnic group, and, especially, age.19, 20 We also show that the GOLD/PP method fails to identify properly about 10% of patients with normal lung function and falsely
Acknowledgments
Author contributions: Dr Miller: contributed data and ideas for the study and to the analysis and writing. He assembled the data set and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Dr Quanjer: contributed ideas for the study and to the analysis and writing.
Dr Swanney: contributed data and ideas for the study and to the writing.
Dr Ruppel: contributed data and ideas for the study and to the writing.
Dr Enright: contributed ideas for the study and to the
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