AlloMap test measures the expression levels of 20 genes from a blood sample and represents the combined expression of these genes as an AlloMap test score.

The European-based CARGO II study was designed to assess the performance and correlation between the presence or absence of acute cellular rejection as determined by examination of endomyocardial biopsy specimens, with results from AlloMap.

The results demonstrated that the mean test scores for samples associated with acute cellular rejection histology grades of = 3A were higher than test scores from samples from patients with no rejection seen on histology.

The results also showed a negative predictive value of 98.4% at the most often used acute cellular rejection threshold.

German University Hospital cardiology and angiology department transplant cardiologist Jorg Stypmann said the surveillance of heart transplant recipients typically has required heart tissue obtained by biopsies to detect asymptomatic acute rejection, which can lead to graft dysfunction or loss.

"We believe that a sufficiently accurate blood test, such as AlloMap, especially in the context of the low prevalence of asymptomatic rejection, can provide a safer alternative to biopsy in stable, low-risk patients," Stypmann added.

XDx’s AlloMap molecular expression test received the US Food and Drug Administration approval in 2008 and CE-mark in 2011.