Sources of variation in forced expiratory volume in one second and forced vital capacity

Abstract

Published prediction equations for lung function differ considerably, but the components of population variation responsible for the differences are unknown.Data were analysed for 6,323 never-smoking adults who did not report wheeze or asthma, from 42 centres participating in the European Community Respiratory Health Survey. Means and components of variance were estimated for males and females aged 20-24 yrs, and the relationships with age and height were examined in those aged 25-44 yrs.Mean lung function for those aged 20-24 yrs differed between centres, but variation could not be wholly attributed to differences in population or equipment. The maximum difference in means by equipment type was 101 mL for FVC in males. Equipment differences were not statistically significant adjusted for country, but differences in mean forced expiratory volume in one second and forced vital capacity by country, adjusted for instrument, were statistically significant in males. Differences between centres in relation to age and height had less influence on predicted values.In conclusion, there are unexplained differences in lung function between ethnically similar nonsmoking symptom-free populations. Neither national reference curves nor those based on the same ethnic group can be guaranteed to give accurate norms of lung health.

Resistência de vias aéreas em crianças medida pela técnica do interruptor: valores de referência

“…The hypothesis that the populations really are different from each other, genetically or regarding general health, has been discussed. (17) These differences observed among results reinforce the importance of using local equations, generated based on healthy controls, in the analysis of clinical studies.…”

Population-specific reference equations?

“…However, we believe it is likely that much of the population heterogeneity in the study by CHINN et al [1] arose from differences in methods, equipment and software. While the authors made some attempts to account for such differences, the level of ''noise'' and the limited site-specific details available (such as quality-control criteria and software versions) would make it hard to demonstrate statistically significant contributions from all sources.…”

From the authors

“…Ethnicity was not recorded in any of the other centres, which are listed in table 1 of our paper [1], but this was not raised as an issue.…”

“…The study by CHINN et al [1] raises awareness of the misuse of reference equations, but offers no realistic alternative. In the meantime, individual laboratories should take every precaution to ensure the reference equations installed in their equipment are appropriate for the population being studied.…”

“…Although our paper [1] is recent, the data were collected in the European Community Respiratory Health Study (ECRHS) I, carried out from 1990-1992, by research teams who had not worked together previously and who came from diverse healthcare systems and different language groups, across four continents.…”