Finding the right tests…
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Finding the right tests…
ELISA
Galactomannan is a sugar molecule found in the cell wall of Aspergillus, a mould that can cause a serious lung infection called invasive aspergillosis in people whose immune system is severely weakened. This test looks for that molecule in a blood sample, using a lab method called the Platelia assay. It's ordered almost exclusively in patients with conditions like leukemia, a recent bone marrow transplant, or prolonged very low white blood cell counts from chemotherapy - healthy people are not tested for this. A positive result supports a diagnosis of invasive aspergillosis alongside imaging and symptoms; a single negative result does not rule it out.
The test reports an index value from your blood sample; most labs treat a result above a specific cutoff as positive. In patients already at high risk - such as those with blood cancers or a stem cell transplant - studies show it correctly identifies roughly 60 to 80 out of 100 true infections, with a similar proportion of true negatives confirmed. Testing the same fluid twice, on separate days, raises confidence in a positive result considerably compared to a single reading. Certain antibiotics and blood products can occasionally cause a false positive.
Galactomannan testing is only useful in people already at meaningfully high risk of invasive aspergillosis - primarily those with blood cancers undergoing chemotherapy, recipients of a stem cell transplant, and people on high-dose steroids or other strong immune-suppressing treatment for a long stretch. In someone with a normal immune system, invasive aspergillosis is rare enough that this test isn't ordered.
A single positive result is treated cautiously, since certain antibiotics, intravenous fluids containing gluconate, and some other unrelated fungi can trigger a false positive. Doctors usually want two positive results from separate blood draws before treating the finding as strong evidence of infection, which raises accuracy meaningfully over a single reading.
- Testing too early, before the fungus has grown enough to shed detectable galactomannan - Antifungal medicine already started before the sample was drawn - Infections limited to one small area of tissue rather than spreading through the bloodstream
Once treatment starts, doctors sometimes repeat this test weekly. A falling level over the first one to two weeks is linked to a better outcome, giving the treating team an early signal of whether the chosen antifungal medicine is working, well before symptoms or scans would show a change.
It means a molecule from the Aspergillus mould's cell wall was found in your blood, which supports a diagnosis of invasive aspergillosis in someone already at high risk, such as after a stem cell transplant. Doctors usually confirm it with a second sample and imaging before treating the result alone as proof.
Yes, certain antibiotics, intravenous fluids containing gluconate, blood transfusions, and some other fungi can occasionally trigger a false positive. This is one reason doctors often ask for two positive results from separate draws before treating the finding as confirmed.
Not on its own. Testing too early in the infection, or starting antifungal medicine before the blood draw, can produce a false negative, so your doctor may repeat the test or add imaging if suspicion remains high.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
It's used almost entirely in people with a severely weakened immune system - such as those with blood cancers, a recent stem cell transplant, or long-term high-dose steroid use - because invasive aspergillosis is rare outside these groups.
There's no fixed fasting rule for this test. Ask your doctor or the centre when you book, especially if it's being drawn alongside other blood work.
A falling galactomannan level in the first one to two weeks of antifungal treatment is linked to a better outcome, so repeat testing gives the treating team an early read on whether the medicine is working. It's tracked until the level becomes undetectable.