Galactomannan use in clinical practice: providing free testing is not the full answer

Invasive aspergillosis is a condition associated with a high mortality rate mostly due to difficulties in performing an early diagnosis. In recent years, galactomannan detection has markedly improved the diagnosis of invasive aspergillosis, but very little is known on how physicians deal with this test in clinical practice.

This cross-sectional study aimed to analyze the indications for the use of serum galactomannan in a large Brazilian hospital, between 2015 and 2016. No specific protocol was in place for GM request. We reviewed the medical records of adult (>18 years-old) patients who were tested for galactomannan due to one the following indications: screening, diagnosis, or treatment follow-up. Additional variables included demographic data, underlying diseases, presence of neutropenia, and use of previous antifungal (anti-Aspergillus) drugs.

The mean age of the patients was 51 years-old (sd±15.8), and 63.3% of patients were male. Patients with hematological malignancies accounted for 60.1% of the cases, mostly acute myeloid leukemia (19.6%). Galactomannan testing was positive in 12.2% of patients, including 1.6% of occasions in which the test was used for screening purposes, 13.2% for diagnosis, and 32.4% during follow-up. Median time for chest imaging request was two days before GM testing. Previous antifungal therapy was reported for 35.1% of patients, mostly amphotericin B (57.1%).

The correct use of galactomannan testing is essential for an early diagnosis of invasive aspergillosis, which may improve the prognosis of the disease. We demonstrated that clinicians usually ask for galactomannan tests to confirm imaging findings in patients who frequently were on antifungal drugs, something that could be improved by medical education. We observed a low frequency of galactomannan use for preemptive antifungal therapy (25.7%), which is worrying considering the well-known beneficial use of GM testing in this scenario.