Restrictive spirometry versus restrictive lung function using the GLI reference values

Abstract

Background: Restrictive lung function may indicate various underlying diseases. The aim of this study was to evaluate the accuracy of different restrictive spirometry patterns (RSPs) to identify restrictive lung function (total lung capacity [TLC] < lower limit of normal [LLN]) according to reference values by the Global Lung Function Initiative (GLI) in a wide age-ranged, general population sample. Methods: A general population sample (n = 607, age 23–72 years, smokers 18.8%) with proper dynamic spirometry and TLC measurements, was included. Accuracy of two main categories of RSP to identify TLC < LLN were evaluated: traditional RSPs (definition 1: FVC < 80% of predicted and FEV1/FVC ≥ 0.7 and definition 2: FVC < 85.5% of predicted and FEV1/FVC ≥ LLN and definition 4: FVC Z-score < LLN) was 5.3%. The most accurate cut-offs for FVC to identify TLC < LLN were 85.5% for FVC% of predicted, and −1.0 for FVC Z-score. The traditional RSP definitions 1 and 2 had higher specificity (95.0% and 96.9%) but substantially lower sensitivity compared to RSP definitions 3 and 4. Conclusion: Based on the GLI reference values, the RSP definition FVC < 85.5% of predicted and FEV1/FVC ≥ LLN, may serve as an alternative with higher sensitivity for screening.