Abstract Background/Aim: Lung function testing is an important measure to diagnose many respiratory disorders. However, their proper interpretation relies mainly on the availability of appropriate reference data. Many reference values are available but most of them are directed to western populations, leaving the rest of the world uncovered despite the established effects of different ethnicity on Lung function tests. Moreover, Very little data are available that can be used as reference values for Saudi people. Therefore, this study was designed to generate prediction equations for respiratory parameters that could be applied for Saudi adult persons. Methods: Three hundred healthy- never smoker adult Saudi students from Tabuk University (150 male and 150 female) with age range 18-25 years were assessed for respiratory functions by oral spirometry. Measured parameters included: Vital capacity (VC), forced vital capacity (FVC), forced expiratory volume first second (FEV1), FEV1/FVC%, forced expiratory flow in mid portion of FVC (FEF25-75%) and maximum voluntary ventilation (MVV). Multiple regression analysis; using sex, height and weight as predictors; was carried out to estimate prediction equations for the respiratory parameters measured. Our results were then compared with data obtained from other studies for Caucasian, African and Japanese ethnic groups. Results: The predicted values for Saudi adults were lower for both male and female subjects than Caucasian, African and Japanese subjects for most of the parameters tested. The greatest difference was obsereved between Saudi adults and Caucasians. However, FEV1/FVC% was higher in Saudi subjects than all other ethnic groups. Moreover, FEF25-75% was higher in male Saudi adults than the other ethnic groups. In addition, in adult Saudi females VC was higher than African and Japanese and lower than Caucasian ones. Conclusions: A considerable difference was found between prediction equations and reference values obtained in the present study and other ethnic groups as Caucasian, African and Japanese. Therefore, pulmonary function reference values and prediction equations were derived for both sexes between the ages 18-25 years in healthy non-smoker Saudi adults. This will provide accurate interpretation for lung functions in this population |
