Objectives: To assess concordance between the fixed 70% ratio cutoff point with the fixed percent predicted values (Fixed-ratio) and the lower limit of normal (LLN) algorithms in interpreting spirometry results in an older population.
Methods: Spirometries were interpreted using Third National Health and Nutrition Examination Survey reference equations for 2319 workers.
Results: The Fixed-ratio algorithm characterized 34.5% (n = 801) results as abnormal, compared with 29.7% (n = 689) by the LLN. There were almost twice as many obstructive and mixed airways spirometries identified under the Fixed-ratio compared to LLN. Rates of restrictive pattern physiology were virtually the same under each algorithm. Overall agreement between the algorithms decreased with age from “almost perfect” for those younger than 60 years to “substantial” for those older than 80 years.
Conclusions: This study found age-related discordance between two algorithms possibly related to the lack of reference equations and standards for individuals older than 80 years.
From the Department of Occupational and Environmental Health, College of Public Health (Drs Mikulski, Sprince, and Fuortes), Department of Internal Medicine (Dr Gerke), Department of Biostatistics, College of Public Health (Mr Lourens), and Roy J. and Lucille Carver College of Medicine (Mr Czeczok), The University of Iowa, Iowa City; and Surveillance Branch (Dr Laney), Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WVa .
Address correspondence to: Marek Mikulski, MD, PhD, MPH, The University of Iowa, 2213 Westlawn, Iowa City, IA 52242 (email@example.com).
This study did not receive funding from any of the following organizations: National Institutes of Health, Wellcome Trust, Howard Hughes Medical Institute. This study did not receive any pharmaceutical or industry support.
The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.
The study was funded by DOE Award No. DE-FC01-06EH06020.
The authors declare no conflicts of interest.