Distinguishing Heparin Contamination from Therapeutic Heparin

Here is an interesting question from Dr Larry Smith at Memorial Sloan-Kettering:

George,

What is the consensus on how to handle samples drawn from a mediport that are obviously contaminated with heparin?  We run a thrombin time to prove that they are contaminated, and request a peripheral draw.  Sometimes we neutralize the heparin with a heparinase when the patients are not on heparin.  Often the medical staff will insist on the result from the contaminated sample and object to recollecting a peripheral draw.  How do we differentiate between a patient who is actually on heparin and the sample is contaminated?

Thanks, Larry.

Thanks for your question, Larry, and apologies for a slow turn-around, as I’ve been traveling and accessing my mail sporadically. I’m sending this one out for review and suggestions from our participants, as I know of no way to distinguish heparin contamination from therapeutic heparin except to ask for a history.  Our folks at UAB essentially use the same approach as you.

It may be that the collectors drawing from the port could use some consultative assistance on how much blood to collect and discard.

Does anyone have a follow-up suggestion? Thank you. Geo