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Medical Forum / General / Laboratory / February 2004High APTT levels
Hello, We are conducting an animal study where we want to measure APTT and PT levels in dogs every week. We have been sending citrated plasma to laboratories that deal with human specimens and have gotten clotting times of >150 for APTT. I have spoken with some vets and they say that taking the sample to human lab should not really make a difference except that the clot detection time needs to be adjusted to an earlier reading (say 5 seconds instead of 10 seconds) since dogs clot faster. Other suggestions include: (1)filling blue-top with blood all the way to the top (2)invert tubes 5X immediately (3)freeze plasma if >2 hours, else put on ice and run test w/i 2 hours The dogs are given tranquilizer before a blood draw so they hold still. There are no anticoagulants given. Can someone give us insight as to why the APTT levels are off the charts? Drugs? Coagulation reagant differences? The dogs are not hemophiliacs; they heal well after surgery. Any help will be greatly appreciated. Sue > Hello, > [quoted text clipped - 16 lines] > Coagulation reagant differences? The dogs are not hemophiliacs; they > heal well after surgery. If the APTTs are ALL high then there is a problem with the samples. Either under or overfilling the sample bottles, or the samples are becoming activated prior to analysis. MB We had similar problems because we were getting coag errors on samples. It appears to the machine it did not clot because it did not detect since it clots prior to the analyzer reading the turbidity. In actuality, the result is probably a "Less Than" instead of a "Greater Than" We use an ACL7000 coag analyzer. If you check your rotors after it gives you a no coag result, check the rotor manually to see if there was a clot formed. If there is, the clot probably formed prior to the analyzer being able to detect the clot. Al > Hello, > [quoted text clipped - 20 lines] > > Sue > We had similar problems because we were getting coag errors on samples. It > appears to the machine it did not clot because it did not detect since it [quoted text clipped - 31 lines] > > > > Sue I would agree with that. Depending on the machine you use, it is always wise to check the optical curve on where it starts and ends up at. The alternative would be to use non optical machines and more mechanical ones such as old fashion fibrometer. I also forgot to mention, we see the same problem with PT's because the times are less than human times. al > Hello, > [quoted text clipped - 20 lines] > > Sue >(1)filling blue-top with blood all the way to the top >(2)invert tubes 5X immediately Those two should not be just a suggestion but are absolutely necessary. I'm a little late getting this thread, but have all pre-analytical variables been examined? I know it sounds stupid, but if the blood was drawn via some sort of lock or catheter, there may be a tiny amount of heparin in the reservior (i.e. standard practice when starting an I.V. catheter without infusing anything is to inject a small amount of heparin into the catheter to keep it from plugging up with a clots, then tubing can be attached later for infusion of saline, etc.) I don't imagine bleeding a dog is easy, nor would starting an I.V., so I was thinking this might be the case in vetrinary medicine also. Perhaps someone else can speak to that. I do, however, remember several occassions where a bad venipuncture caused erroneous results even in the absence of visible hemolysis. Just some random thoughts. > Hello, > [quoted text clipped - 20 lines] > > Sue I know that the human setting on Ca analyzers reads the PTT at 50% completion on the curve. For animals it is usually set at 75%. To make this change for a human lab is not practical and you may not get the results that are right for you.  SignatureDetective Tom Polhaus: " Heavy. What is it?" Sam Spade: "The, uh, stuff that dreams are made of." > I'm a little late getting this thread, but have all pre-analytical > variables been examined? I know it sounds stupid, but if the blood was [quoted text clipped - 33 lines] > > > > Sue > I know that the human setting on Ca analyzers reads the PTT at 50% > completion on the curve. For animals it is usually set at 75%. To make > this change for a human lab is not practical and you may not get the results > that are right for you. We are involved in the Polyheme study involving out in the field infusion of a hemoglobin solution. Samples collected from these patients will all show moderate to severe hemolysis and as a result a limited menu of testing will be done on these patients when they are brought in to the ER. We will be dusting off our old Fibrometers and performing PT and PTT's. If the results on this patients are promising then more labs will have to use old fashion clot detectors instead of optical ones for these patients. there is an instrument on the market that does both automated photo-optical and electro-mechanical. SignatureDetective Tom Polhaus: " Heavy. What is it?" Sam Spade: "The, uh, stuff that dreams are made of." > > > I know that the human setting on Ca analyzers reads the PTT at 50% [quoted text clipped - 10 lines] > on this patients are promising then more labs will have to use old fashion > clot detectors instead of optical ones for these patients. |
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