Decline in 25% to 75% forced expiratory flow as an early predictor of chronic airway rejection in pediatric lung transplant recipients.

BACKGROUND

Bronchiolitis obliterans (BO) is the major obstacle to long-term lung allograft viability. Its clinical correlate, BO syndrome (BOS), is defined as a decline of at least 20% in forced expiratory volume in 1 second (FEV(1)) from baseline. BOS is often diagnosed after significant organ dysfunction has occurred. Because BO is a small-airways disease, we hypothesized that a 20% decline in the 25% to 75% forced expiratory flow (FEF(25-75)) from baseline should occur before a decline in FEV(1) and should predict progression to BOS with high sensitivity and specificity.

METHODS

Pulmonary function tests and records of pediatric lung transplantation patients at Texas Children's Hospital from 2002 to 2007 were reviewed. Declines in FEV(1) and FEF(25-75) from the best post-transplant baseline values were recorded and analyzed. Sensitivity, specificity, and positive and negative predictive values were calculated.

RESULTS

Thirty-one patients were eligible for the study. In 11 BOS patients, the mean±standard deviation number of days from transplant until a 20% decline in FEV(1) was 896.5±400 compared with 728.0±475 (p = 0.022) until a 20% decline in FEF(25-75) was reached. The sensitivity, specificity, and positive predictive and negative predictive values of a 20% reduction in FEF(25-75) in determining BOS were 100%, 90.0%, 84.6%, and 100%, respectively.

CONCLUSIONS

All patients who developed BOS had a decline in FEF(25-75) at or before the decline in FEV(1). The reduction in FEF(25-75) occurred statistically significantly earlier than the decline in FEV(1), by an average of 168.5 days. This decline in FEF(25-75) was also highly sensitive and specific for the diagnosis of BOS.