Substantial variation exists in spirometry interpretation practices for airflow obstruction in accredited lung function laboratories across Australian and New Zealand.

BACKGROUND AND OBJECTIVES: To audit spirometry interpretation practices for airflow obstruction in Thoracic Society of Australia and New Zealand accredited laboratories.

METHODS: Thirty-nine accredited complex lung function laboratories were invited to participate in an online survey. The survey enquired about demographics, definition of lower limit of normal range for spirometry parameters, spirometric parameters used for identifying airflow obstruction, spirometric definition of airflow obstruction, definition of significant bronchodilator response, and chosen spirometry reference equations.

RESULTS: Thirty-six laboratories provided complete responses (response rate, 92%). To define the lower limit of normal, 26/36 used the 5th percentile, 7/36 used a fixed cut-off, and 3 used other. Twenty-nine laboratories utilised FEV1 /FVC as the sole parameter to identify airflow obstruction, 3/36 used FEV1 /FVC and FEF25-75% , and 4 used other. To define airflow obstruction, 25/36 laboratories used FEV1 /FVC < 5th percentile, 9/36 used a fixed cut-off (FEV1 /FVC < 0.7, 6/36; FEV1 /FVC < 0.8, 2/36; FEV1 /FVC < 0.75, 1/36), and 2/36 used other. Twenty-six laboratories defined a significant bronchodilator response as an increase of at least 200mL and 12% in FEV1 and/or FVC, 9/36 used ≥ 200mL and ≥ 12% increase in FEV1 only, and 1 used other criteria. Reference equations utilised for interpretation of spirometry data included: Quanjer GLI 2012 (16/36), NHANES III (8/36), ECCS (8/36), and other (4/36).

CONCLUSIONS: Significant heterogeneity in spirometry interpretation for airflow obstruction exists across Australian and New Zealand accredited lung function laboratories. Lack of standardisation may translate into clinically appreciable differences for the diagnosis and management of common respiratory conditions. Ongoing discussion regarding formal standardisation is required. This article is protected by copyright. All rights reserved.