Category: Screening Assays

Hyperglycemia and Prolonged PTT

From “BJ:” I recently cared for a 60 yr old type 2 diabetic in hyperglycemic hyperosmolar state. Initial serum glucose 960. The partial thromboplastin time (PTT) was initially 78 seconds without clear reason. The international normalized ratio (INR) was 1.4. The prothrombin time (PT) was not initially checked. I felt that the value was likely spurious and I repeated the test a few hours later, with normal result. At that time blood glucose had improved to within the 300s with fluids and insulin. Are you aware of a mechanism whereby severe hyperglycemia can cause the PT/PTT to result artifactually high?
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More on Shortened PTT

From Anita Elledge, MT (ASCP), blood bank/coagulation supervisor, Sierra Vista Regional Health Center, AZ: Our coagulation testing is done on a Stago Compact instrument. The linear range is 20–200 s for the activated partial thromboplastin time (APTT, PTT). We have a policy that any PTT result <22 s must be redrawn, not just rerun the same sample, because it is said that a low PTT result should not occur and is almost always due to a bad collection. I can’t seem to find any documentation that confirms the < 22 s result being a point for this “recollect.” Can you give me a resource for information or any further help with this?

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Pre-Surgical Screening

Prof. Jeanne Isabel, Medical Laboratory Science Program Director, Northern Illinois University, forwarded the following question, posted to the American Society for Clinical Laboratory Science Consumer Forum:

“We run prothrombin time assays with international normalized ratios (PT/INRs) on most all patients pre-procedure regardless of whether they take Coumadin or heparin. I have done some research and this is the general practice but I am wondering if there is a better test. Most of our patients are on Aspirin and/or Plavix or Lovenox rather than Coumadin or heparin. Does the PT/INR reflect the use of these medications or is there a study that would better indicate a risk for bleeding? We do activated clotting times (ACTs) in procedures with the use of heparin. Does that also reflect the anticoagulation affect of Aspirin and Plavix?”

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Ferritin and Prolonged PT/PTT?

From Natalie Shorey, Stago, Inc. Regional Manager, Sydney, Australia:

This clinical case & related question came from the scientists at St George Hospital, one of our teaching hospitals here in Sydney. It prompted some discussion when I put it to other scientists, withour coming to any conclusion so I thought I’d pose the question to you.

A patient has multi organ failure with a grossly elevated ferritin of >99999 ug/mL and the following coagulation profile: prothrombin time (PT), 26.9 s; PT mix, 16.9 s; partial thromboplastin time (APTT) 125 s; APTT mix, 43.8 s ( partial correction), fibrinogen 1.9 g/L; thrombin time (TCT) 87.9 s; D-dimer <20 ng/ml, equivocal lupus, reduced extrinsic and intrinsic factors. Heparin has been excluded as a cause of the elevated APTT. Can the extremely high ferritin level be the cause or someway be attributed to the prolonged APTT?

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Sodium Citrate: 3.8%?

A contributor asks, “has sb reported shorter clotting times when using 3.8% (0.129M) sodium citrate tubes than 3.2% (0.109M) tubes? literature and the logic says the opposite.”

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QQ: Pre-op Screens

A summary of our May, 2013 Quick Question with 57 respondents:

Surgeons typically order pre-operative hemostasis screens. What assays are included in your pre-operative screen?

a. PLT count, PT, PTT: 40 (69%)
b. None, we don’t perform pre-op screen: 8 (14%)
c. PLT count, PT, PTT, TT, fibrinogen: 5 (9%)
d. PLT count, PT, PTT, BT: 3 (5%)
e. PLT count, PT, PTT, TT: 1 (3%)

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POC INRs with an APA

From Elizabeth Kreuser:

Our pharmacy is using a point of care (POC) device to monitor prothrombin times with international normalized ratios (INRs).  However, they have a patient with an anti-phospholipid antibody (APA).  We did a quick study using Stago Neoplastin Cl Plus, Stago clotting factor II, and the POC device. Results were:

Assay                                    Test 1   Test 2
Factor II clotting assay                    17%      14%
POC INR                                         3.5         4.5
Stago Neoplastin Cl Plus INR         2.6         2.8
They are satisfied with the correlation and are going to continue with POC keeping the patient between 2–3, because they feel this will correlate with a 24–45% factor II activity, which is what they want to achieve. I have been trying to find some references and not coming up with much. I think that the numbers are off.  Any advice?

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New Quick Question: Preoperative Screens

George has joined a Laboratory Medicine Best Practices panel whose purpose is to review patterns of preoperative coagulation screening panel usage, in particular, preoperative prothrombin times (PT) and partial thromboplastin times (PTT). We are working on the premise that screening PTs and PTTs fail to consistently predict intraoperative hemorrhage in patients who possess no known coagulopathy, and that the volume of laboratory screening could be reduced and replaced by patient history for a significant savings without sacrificing patient safety. To support the panel’s efforts, I’ve posted a new Quick Question about preoperative screens. Please look it over and give your answer.

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