Spirometer Replacement and Serial Lung Function Measurements in Population Studies: Results From the SAPALDIA Study

Area of Science:

• Pulmonary Medicine
• Epidemiology
• Biostatistics

Background:

• Long-term cohort studies, such as the Swiss Cohort Study on Air Pollution and Lung and Heart Disease in Adults (SAPALDIA), often involve spirometry.
• Changes in spirometer technology over time can introduce measurement bias, potentially affecting the interpretation of lung function trends.
• Previous SAPALDIA data collection waves (1991, 2002) used heated-wire spirometers, while a later wave (2010) employed ultrasonic spirometers.

Purpose of the Study:

• To develop a practical method for controlling spirometer-related measurement bias in longitudinal population studies.
• To derive individualized correction terms for lung function measurements affected by spirometer replacement.
• To compare lung function decline estimates using different correction methods: no correction, fixed correction terms, and individualized correction terms.

Main Methods:

• Spirometer-specific reference equations were constructed using data from healthy never-smokers in SAPALDIA from 1991, 2002, and 2010.
• Individualized correction terms were derived from these equations to adjust for measurement bias.
• Annual lung function decline was calculated and compared across different correction strategies (uncorrected, fixed term, individualized term).

Main Results:

• Spirometer-specific reference equations predicted lower lung function compared to baseline equations.
• Measurement bias increased with participant age and height.
• Lung function decline was significantly different between uncorrected, fixed-term corrected, and individualized-term corrected data, with individualized terms yielding results closest to the pre-replacement period.

Conclusions:

• Ultrasonic spirometers yield lower lung function values than heated-wire spirometers in healthy never-smokers, indicating a substantial measurement bias.
• This bias is significant enough to impact research and clinical interpretations of lung function.
• Future lung function reference equations should incorporate spirometer type alongside anthropometric variables, and the proposed individualized correction method offers a novel solution for cohort studies.