From Bill Chamlee at the Cleveland VA:
Hi George,
I stumbled onto your site while researching the new lower potency heparin/therapeutic range issue. I was interested in your quick question about checking for clots. I don’t do any of the four choices you list. I use two applicator sticks to check for clots after centrifuging and running first. The sticks can act as an activator and my experience is that the PTT is usually shorter after rimming for clots, more noticeably of course in abnormal and therapeutic specimens. And I still don’t understand how you can identify a clotted specimen by looking at the test results. Sure, sometimes the low PTT is a dead giveaway. But not always–the normal looking PTT could really be high. And what if it’s only a PT–INR? I know CAP lists that as an acceptable choice, but I don’t know why. With my method, I have seen plenty of clotted specimens with perfectly “plausible” results. But are they accurate results? I reject them. So does CAP imply clotted specimens are OK if they give plausible results?
And as for visually looking for clots, well between the numerous labels covering our tubes and my old eyes, I am not sure I would see big clots, much less small ones. Yes, it is riskier to uncap each specimen and rim, especially since we have a cap piercer and wouldn’t otherwise have to uncap. And it is also more time consuming and costly. But I am convinced it is the best way to identify clotted specimens for coag testing. I also take a good look at each specimen for total volume and liquid volume (HCT) which could disqualify it and hemolysis in which case we comment. I would be very interested in your feedback on all these issues. Has my OCD gotten the best of me?
Thanks-Bill Chamlee-Cleveland VA
Thanks for your comments, Bill, and welcome to Fritsma Factor. The idea of “visual inspection” has always bugged me, even before our tubes became completely wrapped with labels, who could see a clot well in whole blood? I like your approach, and invite others to chime in with their approach.
I was talking just this morning with frequent contributor Dave McGlasson about applicator sticks and activation. He, like you, is convinced the sticks activate platelets and together we’ve been trying to develop a research plan assessing platelet activation in association with sticks. We’d also like to learn how much platelets become activated by centrifugation, particularly as it relates to preparing specimens for light transmittance aggregometry. Your comment helps confirm our ideas. Geo.
We checked for clots with applicator sticks prior to centrif
We checked for clots with applicator sticks prior to centrifugation until state safety issues came up and result evaluation became acceptable. In my opinion, the potential contact/platelet activation is outweighed by the weight of releasing incorrect results from clotted or partially clotted samples. We have done it for 30 years and it never seemed to create any pre-activation issues. That fact should be a strong consideration as we perform ~100,000 PTTs yearly X 30 yrs = 3 million. As for platelet activation, high speed centrifugation would also activate platelets: as most know, if you attempt to resuspend a spun specimen and perform any platelet testing, by PFA-100 or platelet inhibition studies they are hyperaggregable. Fortunately, platelets are supposed <10,000 for most coagulation testing. R. Dahms
More on the applicator stick question. I wrote the following
More on the applicator stick question. I wrote the following question to Erwin A Vogler, PhD Professor of Materials Science and Engineering and Bioengineering, The Pennsylvania State University Departments of Materials Science and Engineering and Bioengineering Materials Research Institute and Huck Institute of Life Sciences:
I have had several conversations with fellow MLS colleagues about the potential for coagulation activation via wooden applicator sticks, both in the coagulation system and the potential for in vitro activation of platelets. Mr. Stephen Duff and Dr. Diane Jette of Precision BioLogic, sponsor of Fritsma Factor located your current work in the area of contact activation, in particular, your review, Vogler EA, Siedlecki CA Contact activation of blood-plasma coagulation. Biomaterials 2009;30:1857-69.
Would you mind taking a few moments to read our 3/3/10 post, Applicator Sticks, How to Detect Clots and provide us with your opinion about the potential for activation? I contend that our clinical needs are not currently being met by our specimen management procedures and that we need a new, as yet undeveloped approach.
Dr. Vogler’s response:
“My opinion is that applicator sticks certainly do have the potential to activate the plasma coagulation cascade and most probably platelets as well, either by direct contact or as a secondary consequence of plasma activation.
Applicator stick surfaces are very likely to have a variable surface quality (surface chemistry and morphology) and may well differ in the above regard on a batch-to-batch basis. It would not be difficult to quantify the effect in the laboratory using relatively simple surface area titrations of plasma in which clot time of recalcified citrated plasma in contact with variable surface area is monitored. That would take the guess work and opinion out of standard practice.
I hope this response was useful. Best of luck.” Erwin A Vogler, PhD
I agree with Siemens that you should not use applicator stic
I agree with Siemens that you should not use applicator sticks to check for clots BEFORE testing. However, AFTER testing is complete, there is no downside, and I feel it is by far the most effective way to detect a clot. I have seen too many unflagged and plausible results on specimens I have subsequently found to be clotted. We do not have autoverification, but if we did I would still want to know if a result came from a clotted specimen so I could retract it. My applicator stick checks are pretty fast and furious, which probably makes platelet activation even worse, but the results are already determined by then. Thanks to all for a great discussion.
We currently do not check each tube for a clot, however when
We currently do not check each tube for a clot, however when we get a short PTT we re-run the sample and then check for a clot. I am going to re-run a few samples that have been checked with applicator sticks to see if I can see any differences in the clotting times. I, too, would be interested in the platelet activation data. LS
I am intrigued about the question of using applicator sticks
I am intrigued about the question of using applicator sticks to check for clots. There is actually very little information on this issue and needs to be investigated. However, I can offer some findings on the subject. When using the PFA-100 platelet analyzer from Siemens the company advises the laboratory NOT to use applicator sticks to check for clots. They have found that the introduction of a foreign substance, such as material in the applicators sticks, causes a lot of error codes due to the activation of platelets. They have had multiple sites check their citrated blood for clots using the wooden objects. They found that the incidence of error codes and repeats of specimens were a lot higher than labs who did not practice using the sticks to check for clots.
Dave McGlasson
This is quite helpful. I also am not very convinced that loo
This is quite helpful. I also am not very convinced that looking at results does any good. We have run about a dozen clotted samples and the results are everywhere. Some are perfectly normal with normal clot curves. Some PTTs are short with normal PTs. I would be interested in the platelet activation data. I am an old dog and it is difficult giving up checking each tube for clots. But, doing it after running on the analyzer poses issues also. With autoverification, samples would be verified before techs even get a chance to check for a clot. Which then involves corrections in the LIS. Not sure if there is a right answer but keep the opinions coming! KJK