Normal spirometry prediction equations for the Iranian population.

Background: This study aimed to establish normative spirometric equations in a healthy population of Iranian children and adults, and compare these equations with those developed by the Caucasian Global Lung Initiative (GLI) for the first time.

Methods: Spirometric data from healthy Iranian aged 4-82 years sampled in 2019 were used to derive reference equations using the generalized additive model for location (mu), shape (lambda), and scale (sigma).

Results: A total of 418 females and 204 males were included in the study. Applying the GLI standards for the Iranian population resulted from the Z scores of FEV, FVC, FEV/FVC, and FEF was not different from zero. Based on the newly calculated LLN, eleven individuals showed significant values below the LLN for FEV/FVC. In all age groups, this frequency was less than 5%, except for men over 70 years of age, which was 12.5%. There are significant differences between new data and GLI for Caucasian data.

Conclusion: It is recommended that the values and equations generated from this study should be used by physicians and technicians in their routine practice for the diagnosis and assessment of pulmonary disorders.