Defining and Grading an Obstructive Ventilatory Impairment: American Thoracic Society/ European Respiratory Society Interpretive Strategies of 2005 Versus 2022

Background: The American Thoracic Society (ATS) and the European Respiratory Society (ERS) have issued several updates to their guidelines for lung function testing between 2005 and 2022.

Objective: We aimed to compare ATS/ERS recommendations for 2005(R1) and 2022(R2) in defining Obstructive Ventilatory Impairment (OVI) and in classifying its severity.

Patients and Methods: It was a retrospective comparative study including 1129 patients. All patients underwent spirometry with measurement of Forced Expiratory Volume in 1 second (FEV1) and Forced Vital Capacity (FVC). An OVI was considered according to R1 when FEV1/FVC ratio is under the Lower Limit of Normal (LLN) and when the z-score of FEV1/FVC ratio is under -1.645 according to R2. For the severity levels of airflow obstruction: ATS/ERS previously recommended the use of percent predicted FEV1 with 5 levels using cut values of 70%, 60%, 50% and 35%. Recently updated for z-scores with cut values of -2, -2.5 and -4. Mean age was 54.23±19.23 years.

Results: For defining an OVI, both definitions were comparable (529 patients with OVI). For the severity classification, the following proportions were assessed: 151 mild, 86 moderate,84 moderately severe, 133 severe and 75 very severe vs 148 mild, 238 moderate, 76 severe and 67 cases having a normal FEV1 (z-score of FEV1 above -1.645), which were classified as mild according to R1. Mild OVI(R2) were distributed according to R1 into 74 mild, 51 moderate, 16 moderately severe and 7 severe. Moderate OVI (R2) were dispatched using R1 to 10 mild, 34 moderate, 66 moderately severe, 103 severe and 25 very severe. Severe OVI(R2) were classified as 1 moderate, 2 moderately severe, 23 severe and 50 very severe.

Conclusion: ATS/ERS new and previous recommendations seem to be comparable in defining OVI. However, discrepancies were assessed in classifying its severity.