Hemostasis: Lesson 4 - Tests (INR, PTT, platelets, fibrinogen, D-dimer)

Erratum: @8:37, as pointed out by a viewer, somewhat unexpectedly Factor XIII deficiency does not cause abnormalities of either PT or aPTT. In fact, the presence of a clinical bleeding disorder despite normal PT, aPTT, and tests for vWD is an indication to consider checking for XIII activity (though this test is not available in many locations).

I know this is a 9 year old video, but as a Pathology resident studying coagulation testing, this video is gold.

Your videos are excellent! I teach coag to my residents and fellows and will be sending them to your channel for a thorough review. As an aside, Thrombin Time is not generally ordered on the wards, however, it is frequently reflexed in the coag lab as a screen for heparin prior to performing a standard mixing study. Another point, I do think it is worth having discussions with surgeons prior to ordering PT/aPTT testing for patients with no personal or family history of bleeding prior to surgery, as this could be one of the first steps in reducing unnecessary plasma transfusions and their associated risks in otherwise healthy patients (we all have a story of a healthy patient getting plasma prior to a procedure for a lab abnormality with no personal/family hx of bleeding then ending up in the ICU or worse with TRALI). Keep up the excellent work!

Thanks for that. Excellent explanation, as always. I always get frustrated when I (commonly) hear residents freaking out when  a patient w/ alcoholic liver disease has an elevated INR. The literature supports what you said, that  these patients can, in fact, be hypercoagulable. And of course, as far as I know, the INR has only been validated for monitoring warfarin therapy, not in predicting bleeding risk in patient w/ advanced liver disease. I've even heard from some hematologists that fibrinogen would probably be a better test in these patients, absent thermoelastography (TEG or ROTEM), which I guess, are expensive and (still) rarely available.

When YouTube suggested this video I was literally kissing my hands and doing a "My savior" gesture.

I first listened just to review platelet structure and physiology. I have been watching and listening at my desk for tw hours now. THANKS! I will be referring your videos to my students. :)

You, sir, are a Life Saver on so many levels! Thank You!

I'm really thankfull Eric, and I'm starting to love hematology, you should make more lectures about it like approach to anemia, hemorragic syndrome, trombosis, hypercoagulability

As a surgeon, I appreciate this lesson refresher. And your last statement 😄

Salute to you Sir. Your videos gave me not only knowledge but a way to approach problems on a more practical aspect. Please make more videos

I love the series have an exam on haematology and transfusion on Monday. Wish this series was finished before the exam. Fantastic teaching Eric, many thanks.

Very well organized easy to understand video. Best lectures on the topic as alwyas....waiting for next parts....thankyou eric...u r an awesome teacher...

Thank you very much , I suddenly seem to get more out of it this time , your lecture is superb. I heard and read this topic many time in my life but I never remember much out of it. Your lectures is great great.

Thank you very much for this. I am a third year Med Tech student and this will surely help me with my finals this week.

Best lectures on the topic as alwyas....waiting for next parts....thankyou eric...u r an awesome teacher...

Thanks, Eric. I have seen INRs differ lab to lab, within lab for two separate samples in my patients on warfarin. However, I've not seen difference in results by more than 20% which can be huge if INR's over 2.5. I eagerly await your rest of the videos on this topic.

ya this is helping. keep it up. third yr stud malawi college of medicine

Loved it. Preparing for Pediatric Hospital Medicine Boards 2019. Thx

Wonderful Hematology! Things I never know before! Keep it up. Respects from Sindh, Pakistan

Very nice video! I would like to know more about INR. For example: Why the control PT is a geometric mean and not an arithmetic mean? It has some relation to a log scale? Why ISI is an exponent? How exactly is ISI obtained? I think this magnificent series about hemostasis deserves a more detailed video about INR and ISI. Please, at least inform to me where exactly I could get answers for my questions