I (Geo) received this message on 11-27-24 from Dr. Ludwig Albornoz: After a simple search on Google, we landed on your website, regarding a practice of detecting and removing fibrin and or blood clots in clinical laboratory blood specimens by using a mechanical method, either plastic or wooden rods, which I introduced for use in the uncapped sample tube. Would you please share information on the origin of this practice, how extended it may be, if it is considered appropriate, and any particular literature references on the subject.
I’ve contacted several experts to review Dr. Albornoz’s question and none know of any documentation on using wooden dowels (sticks, rods). In follow-up, I’ve made this the topic for our December 2024 Quick Question. Please answer the question on this page and share your comments about clot detection.
Comment from Emmanuel Favaloro, PhD that arrived on 11-30-24: We have used the method of 2 thin wooden sticks to detect clots in whole blood since I started in the lab, over 30 years ago. Some opponents to the method suggest it may promote coag activation, which is possible, but I am not aware of any published study that proves this is a problem, nor do I know the origin of the method; only that it dates at least 30 years. We do not check all tubes for clots, only those that warrant checking, such as indefinite routine clot times.
Dr. Favaloro also checked Google, which gave this very amusing answer via “AI Overview”: “The practice of using wooden applicator sticks to check for clots in blood samples is no longer recommended. This is because it can pose a risk of infection and is difficult to maintain in an automated environment. However, there are other ways to detect clots in a blood sample:” (I’m inclined to take these recommendations seriously when they are supported with documentation.)
- Visual inspection: Gently invert the sample tube and look for clots. You can also inspect the sample in a well-lit area.
- Venous ultrasound: This test uses sound waves to create an image of your veins and can detect blood clots.
- Duplex ultrasonography: This imaging test uses sound waves to look at blood flow in the veins and can detect blood clots.
- D-dimer blood test: This test measures a substance in the blood that is released when a clot breaks up.
on 12-1-24 Mr. David McGlasson wrote: For the Siemens PFA-100 platelet function analyzer, the company advises we avoid applicator sticks. They have found that introducing a foreign substance, such as material in the applicator sticks, causes error codes due to the activation of platelets. They found that the incidence of error codes and specimen repeats was much higher in labs that used wooden sticks to check for clots than in labs that did not.
Given the scenarios of samples with clots after results have been reported, I am curious what folks are doing in those circumstances. Clearly, for some results, the Healthcare providers have already acted, but wondering aloud whether others have a formal process of notification of potential aberrant results and recommend repeat analysis if the results do not correspond to clinical presentation. Ditto for those labs that collect multiple tubes for a panel of tests…what is 1 of 2 tubes are clotted? Reject both, keep the one? Definitely should NOT pool multiple tubes for panel testing (Semin Thromb Hemost 2019;45:433–448.)
Hi George, I am of a similar vintage to Emmanuel and have always used a pair of wooden applicator sticks to clot-check samples—historical teaching from when I was trained 45 years ago. I also tend to break off the ends but the WHS people frown on this now. We do not check all samples, but as part of sample integrity checks before accepting abnormal results. In particular, we clot check INR >4.5 and fibrinogen >4.0 mg/mL. I also teach people to look at the plasma-cell interface (Is it flat?), and to tilt the tube to watch blood flow before running the sticks through. All clues help. During COVID we noted an increase in falsely elevated D-dimer due to partially clotted samples from poor collection technique. Regards, Robyn.
Dr. Ali Sadeghi-Khomami reminded me of our 5-16-24 discussion, Clot Detection by Wooden Sticks which addresses this issue.
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