False-positive Aspergillus galactomannan and its kinetics in allogeneic hematopoietic stem cell transplantation

We evaluated the incidence of and risk factors for false-positive Aspergillus galactomannan (GM) antigenemia in allogeneic hematopoietic stem cell transplantation (HSCT). We also focused on the GM index value and its kinetics.

Patients who underwent their first allogeneic HSCT at our center between June 2007 and December 2012 were included (n = 172). Episodes of positive GM tests were classified as either "true-positive", which fulfilled the EORTC criteria for proven or probable invasive aspergillosis (IA), or "false-positive", which was not accompanied by clinical findings. The remaining cases were regarded as "inconclusive".

The one-year cumulative incidences of IA and positive GM tests were 10.1% and 48.1%, respectively. Among 148 episodes of positive GM tests, 97(65.5%), 23(15.5%), and 28(19.0%) were classified as false-positive, true-positive and inconclusive, respectively. In the first episodes of positive GM tests in each patient (false-positive = 67, others = 30), an increase in the GM value in the first two measurements, neutropenia, and use of anti-mold agents at positive GM episode were associated with a significantly lower possibility of false-positive results according to a multivariate analysis.

A false-positive GM test was frequently seen after allogeneic HSCT. An increase in the GM value may increase its positive predictive value.