Routine pulmonary lung function tests: Interpretative strategies and challenges

Introduction: The diagnosis and management of common chronic respiratory diseases depend on various parameters obtained from pulmonary function tests (PFTs), such as spirometry, plethysmography, and carbon monoxide diffusion capacity (DLCO). These tests are interpreted following guidelines established by reputable scientific societies like the European Respiratory Society and the American Thoracic Society (ERS/ATS). Aim and Methods: This review aimed to offer a comprehensive framework for interpreting PFTs, incorporating the latest ERS/ATS update (i.e.; 2022), and to briefly explore some complex cases to shed light on their implications for understanding PFTs. Results: The ERS/ATS update outlines a systematic approach to interpreting PFT results, which involves several steps. Initially, results are compared to those of a healthy reference population to determine normal, low, or high parameters. Then, potential ventilatory impairments (VIs), such as obstructive or restrictive VIs, are identified, which could indicate specific chronic respiratory or extra-respiratory diseases. The severity of identified VIs or reductions in DLCO is then assessed. If bronchodilator testing is performed, its response is evaluated. Lastly, any significant changes in PFT parameters over time are noted by comparing current results with previous ones, if available. Despite the clarity provided by the ERS/ATS update, certain uncertainties persist and require clarification, such as the identification of new patterns (e.g.; non-obstructive abnormal spirometry, isolated low forced expiratory volume in 1 s), and classifications of mixed VI or lung hyperinflation in terms of functional severity. Conclusion: This review is a comprehensive framework for interpreting PFTs. Since some issues pose uncertainty in clinical practice, it would be beneficial to the ERS/ATS to reconcile some inconsistencies and provide clearer guidance on different classifications and VIs.