Platelet Factor 4 (PF4) Assay for Heparin-Induced Thrombocytopenia (HIT) Screening (Plasma)

What Is Heparin-Induced Thrombocytopenia (HIT)?

Heparin-Induced Thrombocytopenia (HIT) is a condition where your body’s immune system mistakenly attacks platelets (the cells that help blood clot) after exposure to a blood thinner called heparin. This can lead to dangerously low platelet counts and an increased risk of blood clots. HIT is rare but serious and requires careful monitoring.

Why Might You Need This Test?

Your healthcare provider may order this test if you’ve been given heparin (a blood thinner) and your platelet count has dropped unexpectedly, or if you have symptoms like unusual bruising, bleeding, or clots. It’s also used in patients with suspected HIT to guide treatment decisions.

How Is the Test Performed?

A small blood sample is taken from a vein in your arm. The blood is then processed to separate plasma (the liquid part containing PF4) for testing. The test checks for the presence of antibodies that may react with PF4, which can indicate HIT.

What Are the Results Meaning?

Results are qualitative (positive, negative, or indeterminate) and help determine if HIT is likely. A positive result means further testing (like a PF4 antibody assay) may be needed to confirm the diagnosis. Negative results suggest no HIT is present.