If you are experiencing new or worsening respiratory symptoms and have a pre-existing lung condition (like asthma) or a compromised immune system, this test is critical. It checks for the IgM 'first-responder' antibodies your body produces at the start of an infection with Aspergillus, a common mold. A positive IgM result is a strong indicator of an active or very recent fungal infection, not just a past exposure. A simple blood draw is all that is required. This test is essential for your doctor to pinpoint the root cause of your symptoms, ensuring you get the correct anti-fungal treatment right away.