Frequent contributor Dave McGlasson called from the American Society for Clinical Laboratory Science annual meeting venue in San Diego. He has just heard this question from a colleague. "Can you use the chromogenic anti-Xa heparin assay when the specimen is hemolyzed or icteric?" Her concern arose from cases in which patients had been treated with Alteplase (TPA ), causing hemolysis, and now there was an immediate need to measure the unfractionated heparin level to guide reversal.
Hemolysis and bilirubin definitely interfere in the chromogenic assay. Dave's response was that the heparin could still be monitored using the PTT. George adds, given that the patient is presumably in the cardiac catheterization laboratory, the activated clotting time (ACT ) assay may be the answer. George promised Dave to post the question here for your response.
Here is Dr. Kostousov's hemolysis and bilirubin article, cited in his comment below.
Kostousov V, Nguyen K, Hundalani SG, Teruya J. The influence of free hemoglobin and bilirubin on heparin monitoring by activated partial thromboplastin time and anti-Xa assay. Arch Pathol Lab Med. 2014;138:1503–6.