Stitching and switching: the impact of discontinuous lung function reference equations.

In order to distinguish the effects of lung disease from those of normal growth and development, lung function is expressed in comparison with reference data, with forced expiratory volume in 1 s (FEV1) commonly being presented as % predicted. FEV1 % pred has been identified as being of prognostic value in cystic fibrosis (CF), such that an FEV1 of ,30% pred or rapid decline to that level should prompt referral to a transplant centre [1]. Subsequent monitoring of FEV1 % pred after lung transplantation is also important for monitoring graft function and is required to detect any signs of rejection or onset of bronchiolitis obliterans syndrome (BOS), a disease defined as a fall in FEV1 of.20% from baseline determined by the average of two measurements made o3 weeks apart. Continuing to monitor FEV1 % pred after the development of BOS has also been shown to provide important insight into the patient’s prognosis and therapeutic options [2].