Using galactomannan ELISA to detect invasive aspergillosis

The development of an enzyme-linked immunosorbent assay (ELISA) that detects the glycoprotein galactomannan represents an important advance in the diagnosis of invasive aspergillosis. Foy and associates found evidence that the galactomannan ELISA is a highly specific diagnostic tool when used to screen patients who are undergoing hematopoietic stem cell transplantation (HSCT).

They retrospectively studied 121 HSCT recipients who had undergone biweekly screening with the galactomannan ELISA. Thirteen patients (10.7%) had at least one positive test result, and 4 patients had multiple positive results. The test 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. False-positive and false-negative results were less likely to occur in children than in adults.

In 4 of 12 cases of invasive aspergillosis, the galactomannan results were positive before other microbiological results were available. These positive galactomannan results were available before the results of culture and cytological analysis by a mean of 5 days.

The authors say that regular use of this test may result in an earlier diagnosis of invasive aspergillosis in some patients. However, they acknowledge that the test has low sensitivity and a high rate of false-negative results.