Bronchiolitis obliterans syndrome (BOS) is the major obstacle to long-term lung allograft viability. The definition of BOS is a drop of at least 20% in FEV1 from post-transplant baseline not attributable to other causes, according to the International Society for Heart and Lung Transplantation. Unfortunately, the diagnosis often occurs after significant organ dysfunction is present. BOS is a small airways disease, so we hypothesized that a 20% drop in FEF25–75 from baseline will occur prior to a drop in FEV1 in patients who develop BOS. This will allow for earlier diagnosis and intervention.
The pulmonary function tests and medical records of all patients who have undergone lung transplantation at Texas Children's Hospital from 2002 to 2007 were reviewed. Drops in FEV1 and FEF25–75 from baseline were recorded, and means were compared using a paired t test. Sensitivity, specificity, positive and negative predictive value were calculated. IRB approval was obtained from Baylor College of Medicine.
Thirty-one patients qualified for the study. In patients who developed BOS (n = 11), the mean number of days from transplant until a drop in FEV1 was 777.2 days (SD = 378) while the mean number of days from transplant until a drop in FEF25–75 was 666.3 days (SD = 308) (p<0.05). The sensitivity, specificity, PPV, and NPV of a 20% drop in FEF25–75 in determining BOS was 100%, 85.7%, 78.6%, and 100%, respectively.
All patients who developed BOS had a drop in FEF25–75 at or before the drop in FEV1. In these patients, the drop in FEF25–75 occurred statistically significantly earlier than the drop in FEV1, by an average of 111 days. This drop in FEF25–75 of greater than 20% from baseline was also highly sensitive and specific to BOS.
Examining the drop in FEF25–75 can enable one to identify patients who will develop BOS at an earlier stage. This may allow interventions that would prevent BOS from progressing to irreversible stages and might prolong survival after lung transplantation.
Joseph Rosen, No Financial Disclosure Information; No Product/Research Disclosure Information