Objective: To compare several forced spirometry reference equations used in Mexico in order to know which of them have a better fit to a population-based sample.
Material and methods: Spirometric values of 225 healthy subjects 40 years of age or older from Metropolitan area of Mexico City, were compared to several reference equations. The sample is population-based and it was done from June to December 2003. The difference between observed and expected values was calculated. A concordance analysis between both observed and expected values was done and the percentage of subjects under normality lower limit was obtained.
Results: The equations with better fit for FEV1 and FVC were: NHANES III for Mexican-Americans and Euro-Americans; and from PLATINO. Predicted values according to Knudson were lower, and those from Cruz-Mérida, larger than observed values. Percentage of subjects below lower limit of normal was closest to 5% in the reference values from PLATINO.
Conclusions: We recommend the use of reference values from the study NHANES III (for Mexican-Americans or European-Americans) and PLATINO.