2002 OPEN FORUM Abstracts
ESTABLISHING REFERENCE EQUATIONS FOR A PEDIATRIC PULMONARY FUNCTION LABORATORY
Cathy C. Walston, RRT, RPFT, James D. Acton, MD, William D. Hardie, MD. Cincinnati Children?s Hospital Medical Center (CCHMC), Cincinnati, Ohio.
Introduction: Pulmonary Function Tests (PFTs) are important diagnostic tools and outcome measures for disease management. Absolute measures are standardized by conversion to percent-predicted values to account for growth in children. The accuracy and validity of a percent-predicted value depends on the reference equation used, and its ability to compare an individual to the appropriate reference population. Inappropriate reference equations can lead to diagnostic errors and flawed investigative conclusions. We observed that the calculated percent-predicted values for the youngest and shortest children did not correlate well with their clinical pulmonary status or the shape of their flow-volume curve. We sought to identify and implement the most accurate reference equations available based on current scientific evidence.
Methods: We surveyed a sample of U.S. pediatric and adult hospitals to identify the most frequently used reference equations and conducted a scientific literature review related to adult and pediatric spirometry reference sets. After completing the survey and the literature review, reference sets were established based on age and race. We studied spirometry in 12 caucasian males ages six to eight under 120 cms in height performed at CCHMC using the reference equation of Weng-Levinson. We converted the same test data to the reference equations of Wang, Dockery, et al using the same demographic and test date information for each patient.
Results: Significant differences in spirometry were noted in the percent-predicted variables between Weng-Levinson and Wang, Dockery, et al with the largest variations being seen in the FEV1 parameters.
|Patient HEIGHT IN CM||Weng-Levinson||Wang, Dockery et al.|
P value < 0.0001
Conclusion: Significant variability occurs between reference equations for predicted values for pediatric spirometry. Variability can also occur in equation entry between manufacturers. It is important to establish reference equations that are evidence-based, obtained from large sample populations and segmented on the basis of race, gender, height and age.