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Clot Detection by Wooden Sticks

Fritsma Factor participants, a colleague brought up the problem of clotted hemostasis specimens within the context of remote specimen collection. Many facilities recommend checking whole blood specimens with wooden sticks, a policy that has been in place since before 1990 but raises concern for contamination, clot activation, and operator safety. The broad availability of automation may increase the concern for undetected clots but may also provide for electronic clot detection. Please post your comments to Geo at [email protected] or add them to the Comments box below. Thank you!


From Dr. Ali Sadeghi-Khomami 5-16-24: If the frequency changed recently at that site, it could be a specimen collection/transport issue. Here’s what I could find from CLSI H21-V6.


From Dr. Emmanuel Favaloro, 5-16-24: Hi George, Our Westmead laboratory uses these wooden sticks quite a lot to check for clots. We don’t check all tubes; only those we suspect to have clots after visual inspection or after unexpected test results. As for concerns re: (a) contamination–fresh sticks are used, and these are clean, so unsure where contamination comes in; (b) clot activation–we only check when indicated, and if clot found, concerns about ‘clot activation’ is putting the cart ahead of the horse; don’t think the process activates coagulation too much, but I admit we have not undertaken a formal evaluation; (c) operator safety–well, in a diagnostic lab, we are exposed to blood/plasma all the time; might be different in a routine lab if primary tubes are run using a closed system. But then, I’m old school. Been working in the lab for over 40 years with blood, and (touch wood) no evident safety concerns to date. For more detail on the use of the wooden sticks, recommend this reference:

Adcock Funk DM, Lippi G, Favaloro EJ. Quality standards for sample processing, transportation, and storage in hemostasis testing. Semin Thromb Hemost. 2012;38:576–85. doi: 10.1055/s-0032-1319768. PMID: 22706973


From Dave McGlasson, 5-17-24: I have searched online for two hours and I cannot find a study that compares all variables in checking coagulation specimens before they are analyzed visually or using applicator dowels (sticks). Siemens suggests not to use applicators to check for clots on the PFA-100 because they may activate platelets. However, where are the actual studies? This topic is mostly professional opinions or just GOBSAT statements.


From Geo: Checking specimens in response to unexpected results if your equipment samples from primary tube supernatant, but doesn’t work for a reference lab that is receiving plasma. I suspect ongoing education for collectors may be the best answer.

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