Haematology is a branch of pathology, pediatrics, and internal medicine that studies blood, organs forming blood, and blood related diseases. It also studies the causes, ways to detect or diagnose the blood related diseases, possible outcome or recovery of blood diseases, prevention and treatment of this diseases. The hematologist starts its regular work in the management of the laboratory, viewing of specimens in the slide like blood samples and bone marrow samples, analysis of hematological results, and proper caring of in and out patients. In the laboratory of hematology department, hematologist carries out different blood test. They usually perform complete blood count or full blood count (CBC or FBC), erythrocytes sedimentation rate (ESR), and coagulation test which is a very important part of hematology. Coagulation is a compound process in which the blood forms into a solid clot.
Coagulation is very important in the homeostasis of the body. Homeostasis is part of a closed system or open system of living organism, which controls regular and steady condition. It also helps the organism or human to function efficiently or react effectively to different environmental situations. There are certain factors that may affect the homeostasis of the body like acidity, temperature, salinity and nutrients and waste balances. Coagulation usually starts after the damage of a blood vessel. When a blood vessel has been damage, formation of homeostatic plug at the place of injury is being formed by the platelets. This action is called as primary homeostasis. After the action of the platelets, the secondary homeostasis takes place simultaneously which is the formation of fibrin strands that reinforces the homeostatic plug or the platelet plus. Protein in the blood plasma which is also termed as coagulation factor is responsible for the secondary homeostasis.
Different blood related diseases may be prevented, manage and treated properly if detected or diagnosed as early as the first manifestation or sign of the disease. There are different types of blood test that is being performed in the laboratory of hematology department. One of these tests is the coagulation test which is the test of the blood that measures the moment or time of the blood clotting action of an individual under a uniform condition (2007a). Blood clotting action is essential and is also life-supporting. Without coagulation, there will be a large amount of blood loss even on small cuts or wounds but there are also negative effects if the blood clots easily (2007a). This may cause life threatening diseases. If a person has a faster blood clotting ability, there is a great possibility that they might have a life threatening diseases. The following conditions are some of the effects of blood clots in the system or in the internal environment: (a) Blood clots may cause necrosis of the tissues which is cause by the obstruction of blood flow in the arteries.
Blood that flows in the body’s tissue contains oxygen that is essential for its normal function; (b) blood clot may cause an obstruction of blood supply in the deep veins in the muscle. This usually affects the lower legs and occasionally in the lower abdomen which is called deep vein thrombosis. Deep vein thrombosis may cause no trouble at all but the clot that it carries may be hazardous or a threat to their health. When this clot breaks through the veins and travels through the bloodstream, then it will pass through the arteries of the lungs that may cause a great damage or may turn into a life threatening condition such as pulmonary embolism; and (c) heart attack or stroke is also another cause of blood clot. It there is a large clot that passes through the heart or brain and the damage is severe; this may cause coronary embolism or cerebral embolism.
Since there are evidences that prove blood clotting is hazardous to the health of an individual, physician prescribed their patients to undergo coagulation test to evaluate the extent of damages, the clotting time of each individual and other possible clotting problems. The following are the main reasons for ordering a coagulation test: (1) to test if the patient would have bleeding problems during and after their surgery or if it would be risky to undergo surgery; (2) if the patient is having anticoagulant medications, they usually undergo coagulation test regularly to monitor their blood conditions and also as a guide for the physician in prescribing proper dosage of medicines; (3) to identify or detect if the patient has bleeding problems.
Coagulation Test has 3 groups namely: general tests, factor – specific tests, and the lysis tests. The general coagulation test gives fundamental signs of the ability of the blood to clot. This test is used to screen a patient if they have coagulation problem and also to monitor the patients if they are responding to their anti coagulant treatment. Under this group are the following kinds of test: (a) International Normalized Ratio (INR)/ prothrombin time; (b) Activated partial thromboplastin time (APTT or PTT); (c) Bleeding time; (d) Activated clotting time (ACT); (e) Platelet aggregation; (f) Plasma thrombin time; and (g) Plasma fibrinogen.
The second group of coagulation test is the factor specific coagulation test that guides the physician in pointing out which coagulation factor is responsible for the clotting problem. Problems regarding the coagulation factor are mostly inherited but in some cases, they are acquired due to some illnesses. This group of coagulation test includes: (a) one – stage factor assay; (b) thromboplastin generation test (TGT); (c) fibrinopeptide A. The last group in the coagulation test is the Lysis test. This test assesses the method of destruction of the blood clot. Although blood clot is essential in the body, when the damage blood vessels have already healed, the blood clot is usually destroyed when our body releases plasmin. This is an important substance in the destruction process. These are the test under the Lysis test group which is used to assess the destruction process: (a) plasma plasminogen; (b) fibrin split products; (c) protein C; and (d) euglobulin lysis time. Among these three groups of coagulation test, the most commonly used is the general coagulation test.
The following are the most common coagulation test used in the clinical laboratory of hematology department. First is the International Normalized Ratio (INR) or prothrombin time which is used to evaluate the bleeding and clotting propensity of an individual (2007c). This is also used to monitor if the blood thinning drugs like the warfarin (Caumadin) is effective to the patient (2007c). Because of the inconsistency of different laboratories and drugs administered during the test, the World Health Organization develops a method or terms to be used when interpreting hematological results which we called as the INR so that physicians from different laboratories can compare their results (2007a). Warfarin is an example of anti coagulant drug.
This drug is usually prescribed for long term medications especially to those patients that already had a heart attack, deep vein thrombosis, knee replacement and artificial heart valve. The standard prothrombin time last only for 11-15 seconds but there were cases that vary depending on the amount of thromboplastin used (Lohr, 2007). Results of this test may be alter due to some factors like intake of food that is rich with vitamin K like beef, pork, liver, green tea, broccoli, soybeans and others and also medications like antihistamines and diuretics (2007c). Normal results (within 11-15 seconds) mean that the clotting factors VII and X of the patient is still in normal level (Lohr, 2007). If there is an abnormal result or prolonged prothrombin time, it is an indicator that the patient has problems with any of the coagulant factors V, VII, X, lack of vitamin K, disseminated intravascular coagulation or liver disease (Lohr, 2007). If this would be the case or findings, the patient may experience abnormal bleeding.
Activated partial thromboplastin time (APTT) is also called as partial thromboplastin time (PTT). This test measures the time of the formation of the blood clot after a chemical has been added into the collected sample of blood. The clotting process or time should take place between 25 – 36 seconds (Levin, 2007). Physicians would order their patients to undergo this test to assess if the person has a clotting or unexplainable bleeding problem. This is also useful in monitoring the patients with heparin medications (Levin, 2007). Heparin is like warfarin, it is a blood thinner drug. When there is a shorter period of blood clotting in this test, it indicates that the coagulant factor VIII is in a higher level or amount than its normal level (2007d). If the result of this test is not favorable, it shows or it is a sign that the patient may have one of the following problems: (a) malabsorption; (b) hemophilia A; (c) hemophilia B; (d) cirrhosis; (e) hypofibrinogenemia; (f) lupus anticoagulants; (g) disseminated intravascular coagulation; (h) Von Willebrand’s disease; and (i) deficiency in coagulant factor XII (Levin, 2007).
Another test is the bleeding time which is a test for the homeostasis of a body (Lohr, 2006). This also evaluates the platelet functions and its qualitative defects (Lohr, 2006). There are two common methods used to perform the bleeding time test. The Duke Technique which is a stab wound in the earlobe that is 1-2mm deep. Another is the Ivy Technique which is a cut or wound made in the upper arm. The normal bleeding time is within 1 – 9 minutes (Lohr, 2006). The normal time limit for Duke technique is 3 minutes only (Lohr, 2006). Abnormal bleeding time would be categorized here if the bleeding does not stopped for 20 – 30 minutes. This result would be a good indicator that the patient has thrombocytopenia, blood vessel defect, and aggregation of the platelets (Lohr, 2006).
Another test is the activated clotting time (ACT) is a test use to evaluate the clotting time that takes place even with a high dose of heparin especially before, during and after surgery specifically on cases like cardiac catheterization laboratories and CABG surgery (Trimble). Physicians administered anticoagulants especially during surgery to slow down the rate of blood clotting to 400 – 600 seconds (2007a). The study can be done on fresh or citrated blood (Trimble). Activated clotting time is a most effective tool in evaluating the results of heparin medications or therapy. Although ACT is the widely used test for coagulation, there are also some instances that the results are not reliable due to some affecting factors like: patient hypothermia, lysed platelets, protamine sulfate administration and if the equipments used are not warmed in 37 degree Celsius (Trimble).
The platelet aggregation test evaluates the platelets functions like its ability to bind together and form a blood clot (Henningston, 2007). The normal result of this test depends on different laboratories or environment. In this test, it is also possible to determine if the deficiency in your platelets is hereditary or acquired due to other illnesses or side effects of other drugs (Henningston, 2007). The abnormal results of this test signifies uremia, autoimmune disorders, myeloproliferative disorders, storage pool disease, Bernard – Soulier’s syndrome, and Von Willard’s disease (Henningston, 2007).
The plasma thrombin time is the time when a clot is form into a sample of blood when a certain amount of chemical like bovine is placed with the platelet plasma from the patient (2007b). This type of test is used to identify different bleeding disorders and hepatic diseases, and to review the efficiency of the fibrinolytic therapy. The reference time for this test is between 7 – 12 seconds.
Plasma fibrinogen test shows the amount of fibrinogen in your blood (D. and MacArthur, 1999). The liver produces a protein called the fibrinogen which helps in the formation of blood clot. If the result shows high amount of fibrinogen in the blood, possible coronary heart disease will develop if not manage or treated properly (D. and MacArthur, 1999).
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