Bleeding Time (BT)
Bleeding Time (BT)
- This test is done on the patient while he is in the lab.
- No preparation is needed.
- The template (Meilke) method is the most common and considered the most accurate.
- This template is the modified method of Ivy methods.
- The template method gives 1 mm deep incisions.
- A small disposable spring-driven lancet gives a 5 mm long and 1 mm deep incision, giving minimal pain and no scar formation.
- Ivy and Duke’s methods were used in old times.
Precautions for bleeding time (BT)
- This test should be avoided in a patient with a low platelet count.
- A patient with aspirin may have a false positive (raised value).
- Avoid in patients with keloid formation or senile skin changes.
- Avoid in patients who have undergone mastectomy or axillary lymph node dissection.
- Avoid uncooperative patients.
- Extreme body temperature gives false results.
- High body temperature prolonged the result.
- Low body temperature lowers the result.
- Avoid and take the history of drugs that may prolong the result, like patients on anticoagulant therapy, use of salicylates, antibiotics, streptokinase, nonsteroidal anti-inflammatory drugs, and warfarin.
Indications for Bleeding Time (BT)
- This test is done to evaluate vascular and platelet factors.
- Bleeding time gives a better idea about the function of platelets, like the numbers of the platelets.
- This may be done Preoperatively to rule out the possibility of bleeding, e.g., in patients for tonsillectomy, etc.
- But this may not be the routine presurgical procedure.
- This test may be done to evaluate the stability of the patient’s hemostatic mechanism.
- A bleeding test may be done to detect the presence of various coagulation disorders.
- This may be advised to monitor the treatment of active hemorrhage in patients with prolonged bleeding time due to uremia, von Willebrand disease, severe anemia, and congenital platelets functional abnormalities.
Advantages of Bleeding Time
- This test is used to differentiate Von Willebrand’s disease from mild hemophilia.
- This test is useful as a part of the workup for coagulation disorders in patients with H/O excessive bleeding during dental extraction, tonsillectomy, circumcision, and childbirth, even with normal platelets count.
- The bleeding time (BT) is used to find any abnormality of the platelets, either number or function.
The disadvantages of Bleeding Time
- This test is unable to predict excessive surgical bleeding.
- Bleeding time is a crude and not a good screening test for bleeding during surgery.
- The bleeding test will neither predict the likelihood of bleeding nor the likelihood of not bleeding.
- Bleeding time prick is 9 mm long and 1 mm deep, which may give rise to scar formation.
- This test is not recommended to predict bleeding in myeloproliferative disorders and neonates receiving nonsteroidal anti-inflammatory drugs.
- Prolonged bleeding time may not necessarily lead to prolonged bleeding.
Definition of Bleeding Time (BT):
- Bleeding time is the functional test of primary hemostasis.
- This test diagnoses bleeding problems related to the abnormalities of:
- Platelets functions. Platelets response to vascular injury.
- Vascular response to injury.
- Blood vessel elasticity also influences the bleeding time.
- The ability of the blood vessels to constrict.
- Bleeding times is the best single screening test for acquired causes like uremia or congenital functional or structural disorder of platelets.
Bleeding time (BT) facts:
- In the case of platelets 100,000/cmm, the bleeding time is usually normal, but when it is <100,000/cmm, bleeding time is prolonged, and there may be a correlation between the count and severity of thrombocytopenia.
- It measures the length of time bleeding continues after the standardized incision is made in the skin.
- The bleeding time is usually abnormal in congenital defects like Glanzmann’s thrombasthenia.
- Bleeding time is also abnormal in uremia, and the myeloproliferative syndrome is an acquired function abnormality.
- 50% of uremic patients show thrombocytopenia.
- Bleeding in uremia is not usually seen unless the bleeding time is elevated, but some studies don’t agree with this hypothesis.
- Uremic bleeding can be treated by fresh frozen plasma, cryoprecipitate, or desmopressin (DDAVP = 1-deamino-8-arginine-vasopressin).
- Some drugs, like aspirin, also interfere with platelet functions and prolong the bleeding time.
- After the single dose of aspirin, prolonged bleeding time is seen even after 2 hours or less, and maximum effect after about 24 hours.
- Aspirin permanently affects platelets’ function in circulation.
- Platelets’ life span is 7 to 10 days, and about 10% of the platelets are replaced daily.
- After stopping the aspirin, it takes 2 to 3 days, and the range is 1 to 8 days for the production of a new sufficient number of unaffected platelets to make the elevated bleeding time to the normal range.
- Bleeding time may be abnormal in the capillary fragility problem.
- Bleeding time is typically normal in hemophilia and vitamin K or fibrinogen deficiencies but is abnormal in severe cases.
- In general, if the bleeding time is >1.5 times the normal limit, the possibility of excessive bleeding during surgery is increased.
- Bleeding time is basically a screening test for:
- Disorders of platelets function and numbers.
- The integrity of the vascular wall.
Affect of different blood coagulation factors on blood coagulation study parameters:
|Coagulation test||Abnormality of platelets||Abnormality in the intrinsic pathway||Abnormality of prothrombin||Abnormality of fibrinogen or fibrin|
|prothrombin time||No||NO||Very sensitive||Not sensitive|
|APTT||No||Very sensitive||Not sensitive||Not sensitive|
|Blood clotting time||No||Moderate sensitivity||Not sensitive||Moderate sensitivity|
There are four important compartments of the hemostasis:
- Platelets abnormalities are divided into two groups:
- Quantitative when there is abnormal platelets count.
- Qualitative where the platelets functions are abnormal.
- How to predict patient may bleed because of platelets abnormalities:
- If there is a history of aspirin intake or other drugs, it will give rise to thrombocytopenia.
- History of oozing or blood loss due to minor oral or dental surgery, or during menses or easy bruising.
- In case of low platelet count.
Quantitative platelets abnormalities:
|Diseases leading to thrombocytopenia||Causative diseases|
|Platelets distribution diseases||Pooling:
|Platelets destruction diseases||Coagulative consumption:
The blood coagulation phenomenon takes place as follows:
- To vascular injury, the first hemostatic response is in the form of contraction of blood vessels.
- The next phase is the adherence of platelets to the injured vessel and plugs of the damaged area.
- Vasoconstriction (vasospasm). This is controlled by local, humoral, and neuronal factors.
- Initially, there is vasoconstriction, followed by vasodilatation for the influx of the inflammatory cells.
- Formation of platelets plug.
- There are granules discharged from the platelets.
- The platelets aggregates into clumps or plug.
- Then release chemical mediators.
- Platelets are attracted in 15 to 20 seconds to the site of endothelial injury.
- Platelets make plug formation.
- Blood coagulation factors: These coagulation factors are activated and help in the coagulation process.
- Vasculature: There is vasoconstriction (vasospasm).
Functions of the platelets:
- Platelet membrane glycoprotein determines the interaction between the platelets and their external environment.
- The binding of fibrinogen to the platelets leads to platelet aggregation.
- Adherent platelets produce histamine and serotonin will lead to vasoconstriction.
Control of the bleeding:
- Activation of coagulation factors.
- Formation of a clot.
- Clot retraction.
- Clot dissolution (fibrinolysis).
- Failure of any of the above factors leads to prolonged bleeding.
- If the blood vessels have increased fragility, that will also lead to prolonged bleeding time as in old age in a patient with a capillary defect.
- Blood vessel constriction and platelet adherence are not affected by the coagulation system (Intrinsic and extrinsic pathways).
- This test is a sensitive measure of platelet functions and the elasticity of blood vessels.
- Normal platelets count is 140,000 to 340,000/cmm.
- Platelets around 20,000/cmm may have a major episode of hemorrhage.
- It is a crude bio-assay but has become a reliable and sensitive platelet function test by careful standardization.
- Platelets less than 50,000/cmm may lead to prolonged bleeding time.
- Platelets count may be roughly estimated from the peripheral smear, where you will find 10 to 20 platelets /high power field or 1 platelet/20 RBCs is in the normal range.
- Bleeding time more than 10 minutes has a risk of bleeding, and when it is 15 to 20 minutes, bleeding risk may become greater.
NORMAL Values of bleeding g time (BT)
- Bleeding time normal: 2 to 7 minutes
- Borderline: 7 to 11 minutes.
- Abnormal value: 10 to 15 minutes
- Duke ear lobe method = 1 to 3 minutes
- Ivy method = 1 to 9 minutes
- Prolonged bleeding time may be repeated to confirm it. Because if sometimes the large-caliber blood vessel is punctured, then bleeding time will be prolonged.
- Adult, elderly, and pregnant = Template method = 2.0 to 8.5 minutes
- = Ivy method = 1 to 10 minutes
- = Duke method = 1 to 3 method
- Newborn = Ivy method = 1 to 5 minutes
- Child = Ivy method = 1 to 6 minutes
Method for bleeding time:
- It is the most common method where the lancet is used, ensuring a precise surgical incision with a depth of 1 mm. This will give reproducible results.
- Bleeding Time is determined after superficial skin incision and timing the duration of blood flow from the wounded area until it stops.
- A puncture of the forearm after having pressure in the upper arm at 40 mm Hg by blood pressure instrument.
- Clean the volar surface of the forearm.
- Give incision with the template up to 1 mm depth. If possible, give two pricks.
- Avoid any visible vein.
- Now blot the blood till it stops.
- Bleeding time is usually normal in coagulation disorders.
- Bleeding time has limited precision, accuracy, and reproducibility.
longer-than-normal bleeding time may be due to:
- Blood vessel defect.
- Platelet count may be decreased, or there is a defect in their function.
- Thrombocytopenia. Count is <100,000/cmm and usually is <80,000/cmm before bleeding time becomes abnormal.
- Bleeding time is always abnormal when platelets count is <60,000/cmm.
- Platelet count <80,000/cmm = BT is ∼10 minutes.
- Platelet count <40,000/cmm = BT is ∼20 minutes.
- Platelet count <10,000/cmm = BT is >30 minutes.
- Disseminated intravascular coagulation (D I C) where the platelets are consumed.
- Acute Leukemia.
- Coagulation factor deficiencies like Factor I, II, V, VIII, IX, and XI may show some increase.
- Hodgkin’s disease.
- Severe hepatic disease.
- Hemolytic disease of the newborn.
- Patients with uremia where there are a decrease and dysfunction of platelets.
- Patients with anti-inflammatory drugs like aspirin and indomethacin.
- In Von Willebrand disease, the bleeding time is variable. BT is increased out of proportion to platelets suggesting von Willebrand disease or platelet functional defect.
Usually, normal bleeding time (BT)in:
- Severe hereditary hypofibrinogenemia.
- Severe hereditary hypoprothrombinemia.
- Critical values = >15 minutes