The necessity of building population specific prediction equations for clinical assessment of pulmonary function tests

Fitting adequate prediction equations for pulmonary function test (PFT) parameters is crucial in the analysis of lung function tests and their interpretation. Our work aimed at studying the necessity of building population specific prediction equations, rather than using prediction equations built-in in commercial equipment. We used as an example results of studies carried out among Israeli schoolchildren. Second to sixth grade children (7-13 years old), 1064 boys and 1211 girls, were studied in Tel-Aviv. PFT (forced vital capacity, forced expiratory volume in Ist second, peak expiratory flow, forced expiratory flow in 50% volume, forced expiratory flow in 75% volume) performed by these children were adjusted for height, weight and age, for each sex separately, by a multiple regression procedure. Predicted PFT parameters of 300 boys and 301 girls aged 7-13 years, living along the southern shore of Israel, were calculated using the equations built for the same aged Tel-Aviv children as well as the prediction equations built-in in the spirometer used. The ratios between the observed PFT parameters in the southern children and their expected values, using the Israeli population specific equations, were around 1.00. Using the built-in equations resulted in ratios around 0.90. Conclusion The development of population specific prediction equations for PFT parameters is necessary. Such equations should be used both in clinical assessment to minimize misclassification (healthy/sick child) and in epidemiological studies.