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Related Concept Videos

Errors occurring during blood pressure monitoring01:25

Errors occurring during blood pressure monitoring

Blood pressure monitoring is a crucial clinical procedure in diagnosing and managing various cardiovascular conditions. Despite its significance, the accuracy of blood pressure measurements can be compromised by multiple factors, potentially leading to either falsely high or low readings. These inaccuracies are critical as they can significantly impact patient care. So, it is vital to understand these challenges deeply and adopt strategic approaches to minimize errors.
Several factors...
Anticoagulant Drugs: Low-Molecular-Weight Heparins01:30

Anticoagulant Drugs: Low-Molecular-Weight Heparins

Hemostasis is a crucial process that prevents excessive blood loss from damaged blood vessels. It involves various mechanisms such as vasoconstriction, platelet adhesion and activation, and fibrin formation. The importance of each mechanism depends on the type of vessel injury. In contrast, thrombosis is the abnormal formation of a blood clot within the blood vessels, leading to potential complications if the clot obstructs blood flow. Thrombosis can be caused by increased coagulability of the...
Venous Thrombosis III: Interprofessional Care01:29

Venous Thrombosis III: Interprofessional Care

Venous thrombosis requires effective prevention and treatment strategies to improve patient outcomes and reduce potential complications.Prevention StrategiesHealthcare providers must prioritize preventing venous thromboembolism (VTE) for all adult patients upon admission. Interventions depend on bleeding and thrombosis risk, medical history, current medications, diagnoses, planned procedures, and patient preferences. Patients on bed rest should change positions every two hours and, if not...
Therapeutic Index01:13

Therapeutic Index

The therapeutic index of a drug is a key parameter in pharmacology that quantifies the relative safety of a drug by calculating the ratio between the dose that causes toxicity in half the population (50%) to the dose that proves to be effective for half the population (50%). It provides a spectrum of doses for a particular drug ranging from effective to potentially toxic. To illustrate, consider an anticoagulant agent like warfarin. It possesses a narrow window within its therapeutic index to...
Anticoagulant Drugs: Vitamin K Antagonists and Direct Oral Anticoagulants01:18

Anticoagulant Drugs: Vitamin K Antagonists and Direct Oral Anticoagulants

Oral anticoagulants are vital tools in preventing and treating blood clotting disorders. This diverse class of medications can be categorized as vitamin K antagonists, exemplified by warfarin, and direct thrombin inhibitors (DTIs), such as dabigatran, as well as factor Xa inhibitors, including rivaroxaban.
Warfarin, a prominent vitamin K antagonist family member, exerts its effect by inhibiting the enzyme VKORC1 (vitamin K epoxide reductase complex 1). By hindering this enzyme, warfarin...
Effect of Hepatic Disease on Pharmacokinetics: Pathophysiologic Assessment and Liver Function Test01:22

Effect of Hepatic Disease on Pharmacokinetics: Pathophysiologic Assessment and Liver Function Test

In clinical practice, the direct measurement of hepatic blood flow to evaluate liver function presents significant challenges due to the intricate and specialized nature of the necessary techniques. Consequently, healthcare professionals often rely on empirical estimates derived from thorough patient examinations and liver function tests to gauge liver health. Among the tools at their disposal, the Child–Pugh and MELD scoring systems stand out for their ability to categorize and assess the...

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Related Experiment Video

Updated: Jun 12, 2026

The Nijmegen Hemostasis Assay: Simultaneous Fluorogenic Measurement of Thrombin and Plasmin Generation in a Single Well
08:01

The Nijmegen Hemostasis Assay: Simultaneous Fluorogenic Measurement of Thrombin and Plasmin Generation in a Single Well

Published on: February 27, 2026

Falsely elevated prothrombin international normalized ratio values.

Paul Froom1, Mira Barak

  • 1Clalit Health Services, Central Laboratories, Haifa and Western Galilee, Haifa, Israel.

American Journal of Clinical Pathology
|June 17, 2010
PubMed
Summary
This summary is machine-generated.

Elevated International Normalized Ratio (INR) results may be falsely high due to blood draw issues. About one-third of patients with high INR lab tests had normal results upon retesting, indicating a need for awareness.

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Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay
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Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay

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Last Updated: Jun 12, 2026

The Nijmegen Hemostasis Assay: Simultaneous Fluorogenic Measurement of Thrombin and Plasmin Generation in a Single Well
08:01

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Published on: February 27, 2026

Determination of the Procoagulant Activity of Extracellular Vesicle (EV) Using EV-Activated Clotting Time (EV-ACT)
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Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay
13:08

Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay

Published on: September 9, 2012

Area of Science:

  • Clinical Chemistry
  • Hematology
  • Pharmacology

Background:

  • Accurate International Normalized Ratio (INR) monitoring is critical for patients on oral anticoagulation therapy.
  • High INR values increase risks of bleeding complications, while low values raise the risk of thrombotic events.
  • Laboratory staff cannot distinguish between falsely elevated INR results from blood draw issues and genuinely high INR values.

Purpose of the Study:

  • To determine the proportion of patients with INR values exceeding 9 that were falsely elevated.
  • To assess the frequency of patients with INR > 9 in the lab who had INR < 6 upon same-day retesting in the hospital.

Main Methods:

  • Retrospective analysis of laboratory test results.
  • Identification of patients with initial INR readings greater than 9.
  • Comparison of initial INR results with same-day repeat testing values from the hospital.

Main Results:

  • 251 tests showed an INR > 9 (1.84 per 1,000 tests).
  • Of these, 188 tests (74.9%) had an INR of 10 or higher (1.37 per 1,000 tests).
  • 20 out of 61 patients (33%) with initial INR > 9 had repeat INR values < 6.

Conclusions:

  • A significant proportion (33%) of patients with high INR lab results experienced falsely elevated readings due to pre-analytical factors.
  • Efforts should be made to reduce the incidence of these inaccurate INR results.
  • Patients and physicians need to be aware of this phenomenon to manage expectations and prevent dissatisfaction.