Objective: One of the major issues in the use of spirometry is the evaluation of the values obtained in comparison with standardized reference values. Such reference values should be determined by studying populations similar to the population in which they are intended to be used. Considering the anthropometric differences among races and the effect of regional issues, such as climate and air quality, it is recommended that these standards be set and used regionally. The objective of this study was to measure the spirometric values in residents of the Mazandaran province in Iran, as well as to determine which standardized reference values most closely correlate with the values obtained and to devise predictive equations for the target population. Methods: This was a cross-sectional study of 1,499 volunteers, from whom demographic and anthropometric data were collected. After having been instructed in the correct procedure, each volunteer underwent spirometry. From each volunteer, we obtained three spirometry curves that met the acceptability criteria established by the American Thoracic Society. The test with the highest values of FEV1 and FVC was employed in the analysis. Results: We observed significant correlations between the measured values and the reference values, for both genders. The strongest correlations were with the European Respiratory Society reference values and with the 18-20 year age bracket. The predictive equations devised were based on the regression coefficients obtained and the demographic data collected. Conclusions: Our results show that the European Respiratory Society standard is the most appropriate standard for use in the population studied.

Keywords: Spirometry/statistics  numerical data; Climate effects; Reference values; Iran.