Analysis of Blood Coagulation – Diagnostic Tests Example

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"Analysis of Blood Coagulation" is a good example of a paper on diagnostic tests. Thrombin Time is a test usually ordered when some sort of bleeding disorder is suspected in a patient. These bleeding disorders usually occur whenever there is a disorder in fibrinogen and the patient has an increased tendency to bleed due to lack of clot formation in case of an injury  (Nuefeld, 1998). The process of clot formation occurs as a result of an injury when  prothrombin  is released as a result of activation of the coagulation cascade. This  prothrombin  is converted into thrombin which acts on fibrinogen to form fibrin which causes clot formation  (Messick, 2012).   Materials and Methods:   Thrombin used in the practice is of bovine origin which acts similarly to human thrombin.

Fresh plasma samples are obtained bovine thrombin is used in the plasma samples to activate the coagulation cascade. This bovine thrombin would act on fibrinogen in plasma, convert it to its activated form ‘ fibrin’ and form a clot.     Three samples of plasma are obtained for testing. Two test tubes are taken and marked 1. These test tubes are placed in a water bath and the temperature is set to 37 after adding 0.1ml normal saline in them.

After that, 0.1ml plasma is added in the test tubes and then 0.1ml of the earlier obtained and diluted bovine thrombin is added in the sample. A stopwatch is used to note the time of clot formation and the time  is  noted down.     Similar steps are repeated for the remaining samples of plasma and time of clot formation is observed. For samples that did not clot or took a time longer than expected, they are mixed in a ratio of 50:50 with the ones clotting faster and initial steps are repeated while observing the time of clot formation this time.   Results:   Plasma Sample  1  2  3  4  (if done)  50:50 plasma mixes  (specify which combinations)  Time to clot in seconds  15 +17      2      average=16  20+19        2  Average=20  30+35      2  Average=33    1+2  1+3  25+18      2 = 22  average  33+37      2 = 35  average    The results here clearly show that all three plasma samples have increased thrombin time.

The normal range is 10-14 seconds and as we can see that plasma sample 1 is slightly increased whereas samples 2 and 3 have more increased thrombin time.   Discussion:   The test can be performed if there is a suspicion of clotting disorder in the patient.

Use of bovine thrombin helps eliminate fibrin deficiencies in the patient since thrombin is provided which acts on fibrinogen and if clotting does not occur, it can be said that there is a deficiency of fibrin or fibrinogen is unable to activate.     Test 2  Prothrombin  Time  Introduction:   Prothrombin  time is one of the tests used also to check bleeding disorders in a patient. The difference lies in it being able to check the extrinsic pathway of clotting. The test is usually ordered whenever there is an effect of drugs such as warfarin is to be  checked,   a patient is suspected to lack coagulation factors such as in hemophilia and the patient shows abnormal tendency to bleed or abnormal bruising is observed in a patient.     Materials and Methods:   Since this test includes an extrinsic pathway of coagulation, a better understanding of that pathway is required.

The extrinsic pathway for coagulation consists of tissue factor, factor vii, factor X, factor ii, and fibrin  (Tondre, 2010). So it can be performed to observe a deficiency of any of those factors.   Thromboplastin  is the main reagent used in this test along with calcium.

The role of  thromboplastin  here is the activation of the extrinsic pathway  (Laposata, 2011).     The steps of performing this test include: Steps similar to thrombin time are repeated by adding 0.1 ml of normal saline and plasma in test tubes placed in a water bath. After these steps,   thromboplastin  and calcium are added in the test tubes containing plasma. A stopwatch is used to observe the time of visible clot formation. The same steps are repeated for sample numbers 2 & 3 and the time for clot formation is observed.

Those  samples taking longer than expected to form a clot are mixed quickly clotting samples and then the time of clot formation is observed by repeating the steps mentioned above.     Results:   Plasma Sample  1  2  3  4  (if done)  50:50 plasma mixes  (specify which combinations)  Time to clot in seconds  14 +15        2    Average=15  16+16      2    average=16  12+11      2    average=12                The normal range of  prothrombin  time is 12-15 seconds. Sample 3 and 1 have a  prothrombin  time of 12 and 15 seconds which are on the borderline of both low and high ranges whereas sample 2 has a  prothrombin  time of 16 seconds which is a slight increase but can be ignored.     Discussion:   The involvement of  thromboplastin  and knowing that  prothrombin  time involves the extrinsic pathway of coagulation helps us exclude several deficiencies.

Since we know that the extrinsic pathway involves several coagulation factors such as factor X, factor VII, factor II which is also known as  prothrombin  and fibrin help us rule out deficiencies of these factors and hemophilia involving these factors. This test can be used as a simple screening test and complicated tests are required to point out more specifically as to which factor is deficient in the patient  (Kasper, 2005).     Test 3  Activated Partial  Thromboplastin  Time  Introduction:   Activated partial  thromboplastin  time measures the time for a clot to form in the blood just like thrombin and  prothrombin  time but it involves the intrinsic pathway of the coagulation cascade.

This test helps us rule out deficiencies of factors involved in the intrinsic pathway and diseases related to them.   Materials and Methods:   The intrinsic pathway involves clotting factors such as factor VII, X, XI, XII, and factor IX. These factors are deficient in several genetically transferred diseases and may lead to severe bleeding diseases  (Ganong, 2005). Also, certain proteins such as  prekallikrein  and calcium with phospholipids are required in the intrinsic pathway. So this test enables us to find/rule out the deficiency of a wide range of proteins, phospholipids, and clotting factors related to bleeding disorders  (Boon, 2006).     The steps of this test include: two test tubes are obtained but normal saline is not added.   Cephalin  which acts as an alternative phospholipid of platelets in plasma is added in the 0.1ml plasma added already in the test tubes and the test tubes are incubated for 3 minutes.

0.1ml calcium solution is added in the test tubes and time taken for the formation of a visible clot is observed. Similar steps are performed for the remaining samples and the time taken is observed.     Results:   Plasma Sample  1  2  3  4  (if done)  50:50 plasma mixes  (specify which combinations)  Time to clot in seconds  33+32      2  Average=33  39+42        2  Average=41  Negative  Negative    1+3    Negative  negative      Sample 3 showed negative results for activated partial  thromboplastin  time whereas activated partial  thromboplastin  time of samples 1 and 2 are 33 seconds which is normal and that of sample 2 showed a time of 41 which is very close to the normal range of 30-40 seconds.   Discussion:   This test involves the detection of factors involved in the intrinsic pathway of coagulation and helps identify diseases such as DIC, Hemophilia A and B, Von  Willebrand’ s  Disease, and vitamin K deficiency.

Also, this is a simple screening test and more complex testing is required to identify specific factor deficiencies  (Hall, 2013).    

References

HALL, J. E., VAZ, M., KURPAD, A., & RAJ, T. (2013). Guyton and Hall textbook of medical physiology. http://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&AN=816247.

GANONG, W. F. (2005). Review of medical physiology. New York, McGraw-Hill Medical.

BOON, N. A., & DAVIDSON, S. (2006). Davidson's principles & practice of medicine. Edinburgh, Elsevier/Churchill Livingstone.

KASPER, D. L., & HARRISON, T. R. (2005). Harrison's principles of internal medicine. New York, McGraw-Hill, Medical Pub. Division.

TONDRE, R., & LEBEGUE, C. (2010). Handbook of hematology research hemorheology, hemophilia and blood coagulation. New York, Nova Biomedical Books. http://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&AN=350352.

NEUFELD, E. J. (1998). Coagulation disorders. Philadelphia, Pa, W.B. Saunders.

LAPOSATA, M. (2011). Coagulation disorders quality in laboratory diagnosis. New York, Demos Medical Pub. http://site.ebrary.com/id/10488686.

MESSICK, J. B. (2012). Hematology. Philadelphia, PA, Saunders. 

NATIONAL HEART, LUNG, AND BLOOD INSTITUTE, NATIONAL HEMOPHILIA FOUNDATION, & SCRIPPS CLINIC AND RESEARCH FOUNDATION. (n.d.).Biochemistry and Physiology of Factor VIII: Workshop : report.

MONSOUR, P. A., KRUGER, B. J., & HARDEN, P. A. (1986). Prevalence and detection of patients with bleeding disorders. Australian Dental Journal. 31, 104-110.

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