I'm sorry for being so dumb

You are not being dumb. It is a great question!! It helps to provide a full picture. In regards to if the patient is bleeding, has abnormal bleeding or some other issue with bleeding or clotting.

Part of this is platelets. Which tells a lot about clotting, as well as a low/high platelet count can mean a number of things.

It is considered a "routine" lab.

It is not necessarily done on everyone, but it is done pretty routinely.

How do INR and PTT tell you if they are bleeding? I understand H and H, but those ones?

How do INR and PTT tell you if they are bleeding? I understand H and H, but those ones?

PTT has prothombolin time on it--the time it takes blood to clot. Also if memory serves platelet count, again for clotting purposes. If someone is for instance going into surgery, you want to be sure that they will not bleed out or have other complications.

INR--again speaks to how "thin" ones blood is. Thicker-(the lower the INR) and clotting could be a factor. Thinner (a high INR) and one is prone to bleeding heavily. (and this is not medically correct terminology, just as I understand it)

Many people take daily aspirin. Many people take a lot of Ibuprofen. There are certain vitamins and food products that can affect the results.

Bottom line is you want to be sure that whatever you are doing--surgery, looking for an active bleed--whatever the patient is there for, that they are not going to get a clot, or bleed excessively and cause complication.

PTT has prothombolin time on it--the time it takes blood to clot. Also if memory serves platelet count, again for clotting purposes. If someone is for instance going into surgery, you want to be sure that they will not bleed out or have other complications.

INR--again speaks to how "thin" ones blood is. Thicker-(the lower the INR) and clotting could be a factor. Thinner (a high INR) and one is prone to bleeding heavily. (and this is not medically correct terminology, just as I understand it)

Many people take daily aspirin. Many people take a lot of Ibuprofen. There are certain vitamins and food products that can affect the results.

Bottom line is you want to be sure that whatever you are doing--surgery, looking for an active bleed--whatever the patient is there for, that they are not going to get a clot, or bleed excessively and cause complication.

Thank you. That's actually quite helpful.

It is named "CYA medicine", like "cover you a**".

It is true that so many people take anticoagulants nowadays. But:

- platelet number is what it is. A number. It says nothing about functional capacity of the platelets, which can be aggravated by gazillion of factors. Platelet functional tests are not available everywhere.

What we need to know is that if patient takes aspirin, Plavix (and many other pills from this group), pentoxyphilline or other antiaggregants, the platelets will be functionally poor for about 10 days from the last dose. Platelets have half life time of hours, but the total pool renewed rather slow. It matters when patient risks bleeding from "point and sharp" trauma like spinal anesthesia or biopsy. Only one thing to do is to transfuse platelets (extremely expensive and works for 6-8 hours).

Any patient with clinically significant renal failure, acute or chronic, has platelets insufficiency by definition. Number may be normal.

Intrinsic pathway measurement (APTT) is directly increased by thrombin inhibitors (heparin, bivalirudin, argatroban) and to lesser degree short-fraction heparins like Lovenox. It can be used for 1) dosing the drugs above, 2) monitoring of patient with high risk of bleeding, looking for peak caused by increased consumption; 3) monitoring of condition known for increased consumption of factors (DIC, TRALI, sepsis, tumor lysis, post-massive transfusion syndrome). Routine daily monitoring of APTT, unless patient belongs to any of categories above, is controversial and considered CYA.

- extrinsic pathway (PT/INR) is prolonged by warfarin, vitamin K deficiency, hepatic failure, failure of small intestinal absorbtion (whether patient is NPO or not) and consumption as result of increased clotting activity. Monitoring of PT/INR daily or more often is thus justified in many clinical situations. PT is fairly sensitive indicator of liver functional capacities and starts to elevate before bilirubin, so in patients with impending or high risk of failure monitoring justified even q12h.

The most interesting and tragic situation nowadays is a patient receiving ASA and Plavix as "gold standard" for CAD/post PTCA (cannot be really monitored), then Xarelto (direct inhibitor of factor Xa from extrinsic pathway, cannot be monitored as techniques for INR measurement were developed only using vitamin K) as another "gold standard" for stroke prophylaxis in case of afib, and then sq Lovenox as yet another standard to prevent PE during hospital stay ( can be monitored by APTT but not reliable). This patient's coags thus cannot be reliably monitored in any conceivable way, yet all three components of his coagulation system are more or less disabled. It was kinda funny to see three specialist physicians arguing right there about whose blood thinner must be a priority while that poor soul was dragged to ICU with massive retroperitoneal hematoma.