Galactomannan antigen enzyme-linked immunosorbent assay for diagnosis of invasive aspergillosis after hematopoietic stem cell transplantation

Abstract

Invasive aspergillosis is difficult to diagnose in patients undergoing hematopoietic stem cell transplantation (HSCT). In 2003, a serum enzyme-linked immunosorbent assay (ELISA) test for the detection of galactomannan (a glycoprotein found on the Aspergillus cell wall) became available in the United States. In 2004, patients undergoing HSCT were screened biweekly with the galactomannan ELISA at our institution. We performed a retrospective chart review of 121 SCT patients who underwent galactomannan testing. Thirteen of the patients (10.7%) had at least 1 positive galactomannan ELISA, and 4 had multiple positive tests. When calculated in reference to a proved or probable diagnosis of aspergillosis, the galactomannan ELISA had a sensitivity of 0.50 and a specificity of 0.94. The positive predictive value was 0.46, and the negative predictive value was 0.94. Galactomannan ELISA had fewer false-positive and false-negative results in pediatric patients than in adult patients. In 4 of the 12 cases of invasive aspergillosis, the galactomannan ELISA was positive before other microbiologic evidence of aspergillosis was available. In these cases, a positive ELISA predated culture and cytologic evidence of invasive aspergillosis by a mean of 5 days (range, 1-8 days). Our findings indicate that a biweekly serum galactomannan ELISA is a highly specific diagnostic tool for detecting invasive aspergillosis in patients undergoing HSCT. When used regularly, the ELISA may allow for earlier diagnosis of invasive aspergillosis in some patients. The test is troubled by a low sensitivity and high frequency of false-negative tests.