From Heather DeVries, Indiana University Health: We currently perform our platelet aggregations using PRP , but would like to investigate whole blood aggregometry. Our pathologist feels that if we do that, we should also look into lumiaggregometry. He does agree that it would improve our sensitivity to platelet functions disorders (i.e. storage pool disease), but wanted to hear thoughts from other facilities doing the testing. How cumbersome is it to the lab staff? PRP processing is a huge burden with so few people in our special coag lab. What about the expense to the lab? To give you an idea of our volume, we performed 110 aggregations in 2016. Thanks again, Heather.
Hi, Heather, thanks for your question, which gives me the opportunity to express my support for whole blood lumiaggregometry. Our aggregation volume at
UAB parallels yours because we support a number of left ventricular assist device (LVAD
) patients who are on aspirin and Plavix. We use the Chrono-Log 700 Whole Blood/Optical Lumi-aggregometer. I don't mean to recommend any one distributor over another and I receive no
"emoluments," however Chrono-Log is the only manufacturer that supplies whole blood lumaggregometers.
My main points are...
- PRP for optical aggregometry requires at least four 2.7 mL blue-closure tubes to yeild sufficient plasma for optical testing, For whole blood, three tubes is ample, and you can get by on two.
- To prepare PRP you centrifuge using low g-force for at least 15 minutes, then wait 30 minutes for the centrifuged platelets to regain their reactivity. For whole blood, you test as soon as the blood is collected.
- The luminescence channel gives you an unmistakeable indication of platelet secretion (release). In optical aggregation you must tinker with the ADP concentration to produce a biphasic curve. The secretion channel tells you immediately if a storage pool disorder is present.
- In whole blood lumiaggregometry you don't run a PPP blank.
- In whole blood aggregometry, the milieu more closely represents in vivo platelet function than PRP , where the plasma-suspended platelets are affected by mechanical manipulation.
We save a lot of time and energy by avoiding PRP preparation. I see current research publications that still base platelet function testing outcomes on optical aggregometry, and I can't for the life of me understand why researchers don't advance to whole blood. Maybe it is because the instrument cost exceeds the cost of optical aggregometers? The Chrono-log instrument is equipped to perform optical aggregometry when it may be necessary, for instance, when performing ristocetin cofactor assays for von Willebrand disease. Also, epinephrine doesn't work well as a whole blood aggregation agonist, in case your directors insist on epinephrine.
I know several colleagues and friends who swear by optical aggregometry, and I look forward to hearing their responses to this post, but meanwhile, I strongly support lumiaggregometry. Geo.
As I had hoped, I received interesting responses from my colleagues Bob Gosselin and Catherine Hayward, MD, both of whom advocate for optical aggregometry. First from Mr. Gosselin:
Hey GF, et al, not sure I would agree with all your statements, but lumi-agg does have some nice features that could/should be partnered with PRP . The whole blood method is not sensitive with either ADP or epi for lumi release. As you dilute the sample with saline, low platelet counts are problematic. Lumiagg does work well for Glanzmanns, does OK for VWD , but didnt see a BSS when we used that method. It is easier to run, with noted issues about blood volume and prep stuff with PRP. We did have some manufacturing issues with some of their reagents, and the Chronolog AA is awful with challenging reconstitution.
Hi, Bob, thank you for this answer. I checked with Warren Varden, MT (ASCP) who manages our special coagulation laboratory at University of Alabama at Birmingham hospital. Because of our large LVAD service, we run 55–80 aggs per month and have been using Chrono-Log whole blood lumiaggregometers for over 20 years. Some years back the lab hit a record of 18 aggs in one day. Nearly all of our aggs are performed to check for the efficacy of aspirin, Plavix, and ticagrelor (Brilinta). Warren says that although cases of aspirin resistance are rare, many patients require adjustment of Plavix doses, but Brilinta seems to be 100% effective. Our docs also use aggs to check for normal function when these drugs are discontinued, and from time to time the specimen is collected just 3–4 days after aspirin is discontinued, whereupon the platelets are still suppressed.
Warren agrees that the lumi channel gives inconsistent results when using ADP as an agonist and that epinephrine doesn't work at all. Consequently, he doesn't run the lumi channel with ADP , however they do use lumi when testing with arachidonic acid (AA) and thrombin as agonists, where it works well. They really don't need the lumi channel when testing for Plavix and Brillinta efficacy using ADP anyway.
Warren describes arachidonic acid reconstitution as a process involving two solvents, lengthy mixing, and vortexing, as AA is oily, so Bob has a point, however Warren says they've done it so long and so frequently, it is just routine. Warren has experienced no Chrono-Log reagent quality issues, but Chrono-Log has had some periodic disposable probe manufacturing issues.
When the platelet count is over 100,000/uL, whole blood is diluted 1:1 with saline just prior to performing the agg, but in thrombocytopenia with counts below 100,000 the specimen is tested undiluted. Thrombocytopenia is also a limitation when performing optical aggregometry on PRP.
From Dr. Hayward: Interesting dialogue.We abandoned release in whole blood years ago due to poor discrimination between normal and abnormal. As evidence trumps beliefs, I'd encourage you to show/publish your evidence George! Best, Cathy.
I assume Dr. Hayward's comment about poor discrimination addresses the ADP-generated release reaction. Of course, generating a visible biphasic curve in optical aggregometry is also a challenge.
Yes, I agree I should have provided documentation. I have a number of references that support whole blood lumiaggregometry over optical PRP aggregometry, most of which, naturally, are listed on Chrono-Log's web site (click or tap). However, if you will pardon a self-reference, our review, McGlasson DL, Fritsma GA. Whole blood platelet aggregometry and platelet function testing. Semin Thrombos Hemost 2009: 35: 168–80 provides 93 references. I look forward to additional discussion on this issue.