Question

1. Describe the general principle of and sources of error associated with CLIA-waived testing of hematocrit procedures

2. Describe (compare and contrast) the disorders diagnosed or monitored with laboratory coagulation testing

3. Explain how the prothrombin test and INR calculation are used together to monitor coagulations status for a patient.

4. Evaluate the use of platelet counts in coagulation testing

Answer 1

3. Explain how the prothrombin test and INR calculation are used together to monitor coagulation status for a patient.

Answer:

Coagulation tests

• To evaluate the presence of any bleeding disorder like hemophilia, thrombosis, etc.
• To monitor the dose of blood-thinning medications(anticoagulant).
• Liver injury
• To detect any deficiency and defect in the functioning of clotting factors.

Clotting factors participate in the coagulation cascade to clot the blood. There are a total of 20 different coagulation factors present in our body that includes prothrombin, labile factor, thromboplastin, fibrinogen, Stuart factor, etc. Coagulation cascade has two pathways:

• Extrinsic pathway
• Intrinsic pathway

Both of these then merge into a common pathway to complete the clotting process.

The PT test evaluates the clotting factors of the extrinsic pathway that includes factors I (Fibrinogen), II (Prothrombin), V, VII, and X.

Prothrombin time measures how long it takes the blood to a clot that measured in seconds. Different reagents used in different methods for PT, and we get different results.

By Quick's method, 10-14 sec is the PT time.

Internationalized Normalized Ratio (INR)- The ratio of patient's PT to the standardized control PT time.

• Normal value in healthy people - < 1.1
• If the value is >1.1 then, it indicates blood clots more slowly than desired, and a lower INR means blood clots more quickly than desired.
• To standardize results across different laboratories, W.H.O recommended the use of the Internationalized Normalized Ratio (INR).
• Calculated based on the PT test result.
• Allows comparison of results from different laboratories.
• Avoid errors due to the use of different reagents in measuring PT.  
• It is for those people who are receiving anticoagulant medication (blood-thinning) warfarin.

So, PT and INR performed together to avoid any bias.

I hope our explanations are easy to understand. If you like them, encourage us by giving thumbs up.