Aim: Reference equations are prerequisites for interpretation of pulmonary function tests and are important in diagnosis, assessment, and management of a range of respiratory conditions. Such equations should be derived from populations who are closely ethnically and anthropomorphically matched to those in whom the equations will be used. This paper uses measurements from a single cohort of New Zealand adults to derive reference equations for all major pulmonary function tests.
Methods: Detailed pulmonary function test results including measurement of FEV6 and airway resistance were obtained from a cohort of 212 adult New Zealanders of European origin, who were never smokers with no respiratory disease or symptoms. Equations were developed by linear regression, including sex and other candidate variables based on prior univariate analysis. Comparisons between measured and predicted values using the reference equations of the European Respiratory Society (ERS) were made.
Results: Reference equations were produced with high values of explained variance (R2) for many commonly used clinical parameters. When compared with ERS equations, measured values for spirometry and most lung volumes were significantly higher than predicted (mean difference FEV1: male 0.48 L, female 0.36 L, mean difference TLC male 1.14 L, female 0.89 L, SVC male and female 0.66 L).
Conclusions: This study provides a complete set of contemporary pulmonary function reference equations for a New Zealand population of European origin.