Inter-laboratory comparison of flow-volume curve measurements as quality control procedure in the framework of an international epidemiological study(PEACE project)

The aim of this work was to describe the results of a simple quality contro l procedure for the flow-volume curve adopted in a multicentre epidemiologi cal study (PEACE). In 14 centres, 8-15 individuals (n = 157) performed forced vital capacity ( FVC) manoeuvres following a standard protocol with both the local spiromete r/pneumotachograph and a portable spirometer (i.e. the 'reference instrumen t' for this study). Deviances of measurements were assessed by computing th e differences (Delta d) between the former and the latter, the ratios of su ch differences on portable spirometer values (Delta%) and the coefficients of variation (CV). The portable spirometer yielded lower mean Delta FVC and Delta FEV1 (forced in 1 sec) than local instruments (except for two and four centres, respect ively). In most instances, differences were statistically significant. Abso lute mean Delta%FVC ranged from 4.9-18.2%, while Delta%FEV1 ranged from 2.3 -18.5%. The Bland and Altman analysis showed a good agreement between the p ortable and local instruments, except for two centres, where a systematic t rend towards higher individual absolute Delta FVC and Delta FEV1 was observ ed. The overall variability, assessed by CV, was within 6.2% and 5.1% for F VC and FEV1, respectively: it was similar to other quality control studies ranging from 2.0-5.5% for FVC and 2.2-5.8% for FEV1. Our results point out the importance of performing interlaboratory comparis ons as a quality control procedure in multicentre epidemiological studies o n lung function, and of stimulating manufacturers to extend the accuracy an d precision of the instruments.