The FEV1/FEV3 Ratio in Cystic Fibrosis Patients –A Final Marker for End-Stage Lung Disease

Introduction: The forced expiratory volume in 1 second (FEV1) is traditionally the main follow-up parameter for lung disease in Cystic Fibrosis (CF) patients. We examined whether FEV1/ FEV3 volume changes could provide a better benchmark for end stage lung disease, to enable clinicians to make more precise decisions on the optimal time for lung transplantation (LTX).

Methods: A retrospective study charting lung function parameters. The clinical and lung function database (from the medical archives of Sheba Medical Center, Israel) was obtained from the medical files of 22 patients from 2001- 2018 who underwent lung transplantation (LTX) and six patients waiting for LTX. The best annual lung function results for FEV1, FEV3 and FVC.

Results: FVC was more highly correlated with FEV3 than with FEV1. FEV1/FEV3 deterioration emerged in the fifth year prior to the LTX but in the final year, showed a more rapidly accelerating annual decrease. Males presented lower FEV1/FEV3 ratios than females, older patients presented lower values as well, and the Kaplan-Meier survival curve indicated significantly lower LTX rates for patients with a FEV1/FEV3 ratio < 0.7 at the time of ESLD diagnosis.

Conclusion: FEV1/FEV3 captures lung volume changes that can serve as an additional follow- up parameter in CF patients with end stage lung disease. FEV1/FEV3 ratio < 0.7 at the time of ESLD suggests higher survival rates. Consecutive deterioration in this parameter should be considered as a possible indicator for LTX.