Agreement between Spirometers: A Challenge in the Follow-Up of Patients and Populations?

Abstract

Background: Long-term cohort studies and lung function laboratories are confronted with the need for replacement of spirometers. Lack of agreement between spirometers might affect the longitudinal comparison of data, notably when replacing conventional by portable spirometers. Objectives: To compare the handheld EasyOne (EO) with the conventional SensorMedics (SM) spirometer, and to analyze the interdevice reproducibility of EO spirometers. Methods: In total, 82 volunteers completed spirometry sessions with 1 SM and 2 of 3 EO spirometers following a Latin square design. Analyses of differences in forced vital capacity (FVC), forced expiratory flow in 1 s (FEV₁), FEV₁/FVC and mean forced expiratory flow calculated between 25 and 75% of the FVC between spirometers used a mixed effect model with a random intercept for each subject and the effect of the device as fixed effect adjusted for sex, age, height and order of spirometer tested. Bland-Altman plots show the 95% limits of agreement. Results: Comparisons between EO and SM showed relatively small mean differences of <3%, but systematically lower values for FVC and FEV₁ in all EO devices. The 95% agreement exceeded the limits for FEV₁ by 50 ml in 2 EO spirometers. The EO interdevice comparisons showed mean differences and limits of agreement within established thresholds, thus indicating fair accuracy when comparing devices. Repeats with the same spirometer did not result in statistically significant differences. Conclusions: This study suggests fair agreement between the handheld and the conventional spirometer. Differences slightly exceeding limits for FEV₁ in 2 EO devices might be considered mostly irrelevant for clinical practice. However, the systematically lower FVC and FEV₁ observed with EO may be significant for epidemiological studies, thus justifying inspection before replacing devices.

A pilot study of hot-wire, ultrasonic and wedge-bellows spirometer inter- and intra-variability

“…Nevertheless, the systematically higher values for FVC and FEV1 for hot-wire and wedge-bellows compared to ultrasonic spirometers suggest that there are actual differences in measurements between the different types of instruments. Similar, but smaller differences have been observed in previous studies of other hot-wire and ultrasonic spirometers [ 5 , 6 ]. A strength of our pilot study is the inclusion of the Vitalograph, which is considered a gold standard in spirometry testing as it measures volume directly [ 13 ].…”

Adult lung function and long-term air pollution exposure. ESCAPE: a multicentre cohort study and meta-analysis

“…As common in long-term lung function studies, spirometry devices had to be updated with new software or replaced during follow-up. Such changes can be an inherent source of differences in the measured lung function and its temporal change [ 28 ]. The inherent limitations in exposure assessment are also amplified in the longitudinal analyses.…”

Short-term air pollution exposure decreases lung function: a repeated measures study in healthy adults

“…A homogeneous study population reduces between-individual variability and further increases statistical power; the longitudinal study design (within-subject repeated measures) improves statistical efficiency by reducing potential confounding by personal characteristics that do not vary over time. Spirometry measurements were always made with the same instrument and on the same time of day (8 am–10 am), which excludes between instrument and within-day variations in pulmonary function [23, 24]. In addition, the subjects were unaware of the objectives of our the study, which makes participation bias very unlikely.…”