Screening Assays

PT % Activity

This came up in correspondence yesterday and challenged an assumption. The PT is reported in seconds and INR, of course, and it was previously reported as the PT ratio (PTR), which is defined as a ratio of the patient’s PT to the mean normal PT (MNPT). But what is the PT % activity? I have […]

Screening Assays

MELD Score and INR

The model for end-stage liver disease (MELD) score attempts to objectively assesses the severity of chronic liver disease and prioritize liver transplants. The MELD formula is: MELD = 3.78×ln[serum bilirubin (mg/dL)] + 11.2×ln[INR] + 9.57×ln[serum creatinine (mg/dL)] + 6.43; where ln = natural log. MELD score is used to assess 3-month mortality: <9 = 1.9%; […]

Screening Assays

Reference Intervals in Multiple Sites

George received a question from a colleague who is preparing to establish a PT reference interval (RI) for a series of laboratories, large and small that use coagulometers with a range of sophistication from a single manufacturer. All the labs will use a single PT reagent from the manufacturer who distributes the instruments. The key […]

Screening Assays

HCT >55% and Citrate Volume Adjustment

George, is there research available now that states a HCT >55% will not interfere with PT or PTT results? We struggle with the CAP requirement. We use a mechanical based method for PT and PTT within our organization. Hello, and thank you for your question. The current CLSI guideline, Adcock DM, Hoefner DM, Kottke-Marchant K, […]

Screening Assays

Thrombin Time Technique

From Monali Gupta MD, Toronto General Hospital: Hi George, I compliment you for creating such a wonderful website to understand and learn coagulation. The modules are very educative. I have two questions about the DTI assay described in Module 28, Thrombin Time Assay. Why patients’s plasma is diluted in 1:8 or 1:20 in saline? Why pipetting has […]

Anticoagulant Therapy

Correction for HCT >55%

Joan Chapman sent this question. Our institution corrects for HCT greater than 55% for routine and special coagulation assays. It has been our observation, however, that occasionally a patient sample will have a normal PT and PTT in spite of a high crit. We have had a policy that states if the PT and PTT […]

Screening Assays

Promacta and Brown Plasma

From John Mitsios, MD at Cornell. Hi George! I had a question regarding the effects of eltrombopag (Promacta®, a TPO stimulating agent), which is typically given to patients with immune thrombocytopenic purpura (ITP), on routine coagulation assays. The reason for this question is that it has been observed in some patients that at high doses the plasma […]

Bleeding Disorders

Pre-surgical Screening Reprise

I’d like to draw your attention to some recent responses to the November 8, 2013 post by Jeanne Isabel entry about pre-surgical screening.

Screening Assays

Factor VII Padua Mutation

As a followup to the July 30 Discordant PT Results, George presented this problem to a colleague in the booth of one of the major hemostasis materials distributors in the Clinical Laboratory Expo, thereby “spoiling his day.” Nevertheless, he had the answer by days’ end, confirming the response posted by Dr. Vadim Kostousov. This was further confirmed […]

Screening Assays

Discordant PT Results

George is attending the annual AACC meeting at McCormick Place in Chicago. A colleague described a puzzling case in which a patient has a prolonged prothrombin time (PT) using a 1.3 ISI thromboplastin reagent (Stago) and a normal PT when using Dade (Siemens) Innovin. The findings are consistent on repeat split specimens, the PTT is […]

Screening Assays

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George Fritsma is a medical laboratory scientist, educator, and author. George is a member of the International Society on Thrombosis and Hemostasis, the International Society for Laboratory Hematology, and the American Society for Clinical Laboratory Science.

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