Introduction There have been always controversies whether, there is a hypo or hyper diagnosis of COPD according GOLD criteria with parameters driven many years ago, around many countries.
Purpose The purpose of our study is the use of mathematical models for the comparison of Greek patients with COPD, according GOLD criteria versus normal values of our country.
Methods Using spirometry results from a pool of healthy local population (n = 500, age range 18–89 years) we fitted regression models, separately for men and women, for FEV1 and FEV1/FVC ratio. The set of healthy individuals consisted of 261 women (52.2%) and 239 men (47.8%). Their mean age (SD) was 48.20 ± 17.19 and 46.92 ± 16.16 years respectively. The corresponding heights were 162.7 ± 7.2 and175.8 ± 7.3 cm. Predicted normal FEV1 was also calculated using the European Coal and Steel Community (ECSC) equations. Also 124 subjects, with a history of COPD were studied (age range 25–91 years).
Results A positive and linear association with height was apparent in women whereas for men, a guadratic height term was also statistically significant. Predicted FEV1 of healthy individuals, based on either the ECSC or the locally derived equations, was excellent with the concordance correlation coefficients being 0.986 for women and 0.991 for men (p < 0.001 in both cases). Using the GOLD 2008b staging definitions and the ECSC predicted FEV1, the obstructive individuals were classified as having mild (17; 13.71%), moderate (48; 38.71%), severe (40; 32.26%) and very severe (19; 15.32%) COPD. The corresponding figures for the same classification, based on our derived equations for FEV1, were 17 (13.71%), 44 (35.48%), 42 (33.87%) and 21 (16.94%), respectively. The overall agreement between the two classifications was 97.85% with the kappa coefficient of agreement indicating a very good agreement (kappa = 0.936; p < 0.001). Out of the 124 obstructive individuals, 4 (3.2%) were found to have an FEV1/FVC ratio which was above the LLN as predicted from our equations.
Conclusion The statistical analysis has shown a high correlation between the parameters already used and those locally derived.