PPR 6340 Hematology and Coagulation

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Questions and Answers

What does Prothrombin Time (PT) primarily measure?

Level of vitamin K in the blood

Activity of factors II, V, VII, and X (correct)

Effectiveness of anticoagulants

Activity of all clotting factors

What is the normal range for Prothrombin Time?

12 seconds (correct)

10 seconds

8 seconds

15 seconds

What is the purpose of the International Normalized Ratio (INR)?

To standardize Prothrombin Time results across different laboratories (correct)

To measure the d-dimer levels in blood

To calculate the therapeutic level of enoxaparin

To assess the overall clotting ability of the patient

What therapeutic range is commonly targeted for INR in patients on anticoagulation therapy?

2-3 (A) Signup and view all the answers

In evaluating the therapeutic effect of enoxaparin, which specific test should be considered?

Activated Partial Thromboplastin Time (aPTT) (C) Signup and view all the answers

What is the normal range of Mean Corpuscular Volume (MCV) for red blood cells?

80-96 fL/cell (D) Signup and view all the answers

What type of anemia is indicated by a mean corpuscular volume (MCV) of less than 80 fL?

Microcytic anemia (B) Signup and view all the answers

Which of the following correctly describes the normal hemoglobin range for men?

13.8-17.2 g/dL (B) Signup and view all the answers

What is the significance of an increased reticulocyte count?

Indicates acute blood loss or hemolysis (B) Signup and view all the answers

Which component of the red blood cell indices is not typically used in clinical settings?

Mean Corpuscular Hemoglobin (MCH) (D) Signup and view all the answers

What would the hematocrit level have to be for it to fall within the normal range for women?

36.1-44.3% (A) Signup and view all the answers

What are the symptoms commonly associated with anemia?

Weakness, fatigue, and shortness of breath (C) Signup and view all the answers

Which vitamin deficiency is most commonly associated with macrocytic anemia?

Folate (B) Signup and view all the answers

What is the purpose of measuring the activated partial thromboplastin time (aPTT)?

To measure activity of intrinsic and common coagulation pathways (A) Signup and view all the answers

Which factor does low molecular weight heparin (LMWH) preferentially inhibit?

Factor X (A) Signup and view all the answers

Which of the following is true regarding the normal range for aPTT?

Normal aPTT is typically around 30 seconds (D) Signup and view all the answers

When should anti-Xa levels be ordered for patients on low molecular weight heparins?

For patients with acute kidney injury, morbid obesity, or who are pregnant (A) Signup and view all the answers

What does a D-dimer test measure?

A breakdown product of fibrin in clot formation (A) Signup and view all the answers

What is the expected outcome after a patient starts intravenous heparin infusion?

aPTT should be 1.5-2.5 times the control value typically (A) Signup and view all the answers

Which statement is accurate regarding the interpretation of the aPTT test?

High variability can lead to interpretation challenges (A) Signup and view all the answers

In what situation would a D-dimer test most likely be ordered?

To rule out venous thromboembolism (VTE) (B) Signup and view all the answers

Study Notes

Hematology and Coagulation

Hematology and coagulation are covered in PPR 6340 Clinical Laboratory Medicine
Objectives include defining red blood cell indices and their interpretation, describing the coagulation cascade, defining common laboratory tests for coagulation, and understanding situations requiring specific testing for drugs.

Red Blood Cells, Hemoglobin, and Hematocrit

Another name for a red blood cell is a "corpuscle."
Red blood cells transport oxygen.
Normal red blood cell counts are 4.7-6.1 x 10⁶/µL for men and 4.2-5.4 x 10⁶/µL for women.
Hemoglobin (Hgb) is the oxygen-carrying molecule.
Normal Hgb levels are 13.8-17.2 g/dL for men and 12.1-15.1 g/dL for women.
Hematocrit is the percentage of red blood cells (RBCs) in the blood.
Normal hematocrit levels are 40.7-50.3% for men and 36.1-44.3% for women.

Red Blood Cell Indices

Mean Corpuscular Volume (MCV) estimates the average volume of a red blood cell (RBC).
Normal MCV range is 80-96 fL.
MCV can be calculated by dividing hematocrit by RBC count.
Mean Corpuscular Hemoglobin (MCH) represents the average amount of hemoglobin within a red blood cell.
Normal MCH range is 27-33 pg/cell.
Mean Corpuscular Hemoglobin Concentration (MCHC) is the average concentration of hemoglobin in a red blood cell.
MCHC is calculated by dividing hemoglobin by hematocrit.

Anemia

Low hemoglobin is associated with symptoms such as weakness, fatigue, and shortness of breath.
Reticulocyte count measures immature red blood cells, increasing in conditions like acute blood loss or hemolysis.
A decreased reticulocyte count suggests deficiencies in iron, folate, or vitamin B12.
Identifying the Mean Corpuscular Volume (MCV) aids in characterizing anemias
Lower MCV indicates microcytic anemia (commonly caused by iron deficiency), while higher MCV indicates macrocytic anemia (commonly caused by folate or vitamin B12 deficiencies).

Coagulation Cascade

The coagulation cascade describes the process of blood clotting
The coagulation cascade has intrinsic and extrinsic pathways that converge on a common pathway.
Key players in the pathway include factors I (fibrinogen), II (prothrombin), V, VII, VIII, IX, X, and XIII.

Activated Partial Thromboplastin Time (aPTT)

aPTT measures factors VIII, IX, XI, and XII in the intrinsic pathway and the common pathway (factors II, V, and X).
It is used to monitor heparin therapy and some direct thrombin inhibitors.
Measured in seconds.
Variability between labs is high.
Normal range: ~30 seconds (control value).
Historically, aPTT goal was 1.5-2.5 x control value (45-75 secs)
aPTT needs to be established and should be consistent throughout the testing process.

Low Molecular Weight Heparins (LMWHs)

LMWHs (e.g., enoxaparin, dalteparin) primarily inhibit factor X.
Anti-Xa levels are used to monitor LMWHs, not aPTT.
LMWH dosing needs to be adjusted based upon clinical status.

D-Dimer

A breakdown product formed during clot formation.
Used to screen for suspected blood clots, including deep vein thrombosis (DVT) and pulmonary embolism (PE).
Normal range is typically <0.5 mcg/mL.
Highly sensitive but nonspecific.

Prothrombin Time (PT)

PT is a measure of factors II, V, VII, and X activity.
Measured in seconds.
Normal range: approximately 12 seconds (control value).
Used to monitor warfarin therapy.

International Normalized Ratio (INR)

INR is used to standardize PT results across different labs and reagents.
Calculated by the lab from the International Sensitivity Index (ISI), provided by the reagent manufacturer.
A normal INR is usually 1.
Therapeutic ranges for INR vary by indication (e.g., common ranges 2-3).

Case Studies

Case studies of patients with various conditions involving hematology and coagulation are discussed.

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Description

This quiz focuses on hematology and coagulation as outlined in PPR 6340 Clinical Laboratory Medicine. It covers key topics such as red blood cell indices, the coagulation cascade, and the interpretation of laboratory tests. Understanding these concepts is essential for effective clinical practice in laboratory medicine.