Top News 8/27/09
Lung Allocation Score Improves Transplant Likelihood, But Mortality Still High
Implementing a system based on the lung allocation score (LAS) has improved the likelihood of lung transplantation for individuals with idiopathic pulmonary arterial hypertension (IPAH), but mortality on the waiting list is still high when compared with lists for other major diagnoses, according to new research out of the University of California San Francisco which appears in the September 1 issue of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.

"Most people will agree that the LAS has improved organ allocation for most patients on the waiting list, but we wished to study how it has specifically affected patients with idiopathic pulmonary arterial hypertension—a condition for which the LAS may not adequately capture the severity of the patient's illness," Hubert Chen, MD, MPH, assistant professor of medicine at UCSF and lead author of the study, said in a statement.

In the study, investigators reviewed data for nearly 8,000 US registrants diagnosed with COPD, IPF, CF, or IPAH between May 4, 2002, and May 3, 2008; the team examined two outcomes—death versus transplant, comparing the "pre-LAS" period (from May 4, 2002, to May 3, 2005) with the "post-LAS" time (from May 4, 2005, to May 3, 2008.)

In addition to the expected finding that the implementation of LAS was associated with an overall increased likelihood of transplantation and decreased risk of death, according to the report, investigators also discovered that the risk of death for each individual disease decreased significantly—with the exception of IPAH.

"The fact that the LAS has led to an overall improvement in the time to transplantation is not particularly surprising," noted Chen. "But we would hope that those changes would have positively affected all lung transplant candidates, whereas we found distinct differences in the impact according to disease, particularly for pulmonary arterial hypertension."

The authors write that one possible explanation is that key prognostic indicators in IPAH are not considered under the LAS algorithm.

"Hemodynamic variables currently included in LAS, such as pulmonary capillary wedge pressure, provide little information for patients with IPAH," wrote Chen. "In contrast, mean right arterial pressure and cardiac index, which are known to be strong predictors of mortality for patients with IPAH, are not utilized."