Bleeding Time: Duke's Method

• Bleeding time is the duration from skin puncture to the cessation of bleeding.
• It indicates the effectiveness of plug formation and vasoconstriction.
• Normal bleeding time ranges from 1 to 5 minutes.
• Bleeding time is determined using Duke's method.

Duke's Method

• Bleeding Time (BT) is measured as the interval between skin puncture and spontaneous, unassisted stoppage of bleeding.
• The BT test assesses platelet function in vitro.
• The function of platelets and the integrity of capillaries are determined from the length of time required for bleeding to stop after a deep skin prick.

Apparatus

• Equipment needed for the sterile finger prick includes:
  • Whattman's filter paper
  • Stopwatch
  • Lancet

Procedure

• Clean the finger with spirit and allow it to dry.
• Make a deep skin prick, then immediately start the stopwatch.
• Blot the blood drop on filter paper every 15 seconds, placing subsequent drops further on the side of the filter paper.
• Number the blood spots from 1 onwards and handle the finger gently.
• Stop the stopwatch when bleeding ceases, and note the time and count the blood drops n the filter paper.

Precautions

• Avoid rubbing the finger tip, as it increases blood flow and alters bleeding time (BT).
• Avoid squeezing the finger.
• If bleeding continues after 10 minutes, stop the test and apply pressure to the wound site.
• Do not press the filter paper on the bleeding spot to avoid interfering with bleeding.

Conditions with Increased Bleeding Time

• Thrombocytopenia (platelet count < 50,000/mm3)
• Thrombasthenia (platelet function abnormality)
• Von Willebrand disease (factor VIII deficiency + Platelet defect)

Clotting Time

• Clotting time is the interval between skin puncture and formation of a fibrin thread.
• It tests the clot mechanism.
• Normal clotting time ranges from 2 to 8 minutes.
• Clotting time can be determined by the capillary glass tube method.

Capillary Glass Tube Method

• A deep skin prick is made and blood is taken into the capillary glass tube.
• The time taken until blood clots, which is detected by the appearance of a fibrin string, is recorded.

Apparatus

• A lancet is required.
• A stopwatch is needed.
• A capillary glass tube about 10-12 cm long with a uniform bore diameter of 1-2mm is required.

Procedure

• Make a sterile finger prick of 3 mm in depth and start the stopwatch immediately.
• Allow blood to flow into the capillary tube, maintaining body temperature by holding the tube between the palms.
• After 2 minutes, break off the capillary tube 1-2 cm from the end every 30 seconds and look for the appearance of fibrin string to check blood clots.
• The clotting time is indicated when a thin fibrin string spans a gap of 5mm between two ends of the broken capillary tube, and stop the watch and record the time.
• Normal clotting time by capillary tube method is 2-8 mins.

Precautions

• The prick should be deep enough that blood flows spontaneously.
• Hold the filled capillary tube between palms immediately to maintain body temperature.
• A fibrin string must be looked for each time the capillary tube is broken

Review Questions

• Alternative bleeding time tests include the Ivy method and capillary fragility test of Hess.
• Alternative clotting time tests include the Lee White (venipuncture) method and the Drop method.
• Bleeding time and clotting time tests are used in individuals with frequent/persistent bleeding from injuries or a family history of bleeding disorders.
• They are done before every minor and major surgery and before and during anticoagulant therapy.
• These tests are done before taking biopsy from BM, liver, and kidney or in patients with liver disease.
• Clotting time is longer than bleeding time in normal individuals because bleeding time measures the formation of a temporary hemostatic plug while clotting time measures the formation of a definite hemostatic plug that involves a complex cascade of reactions.
• Prolonged bleeding time with normal clotting time can be seen in Thrombocytopenia, Thrombasthenia, Von Willebrand disease, vessel wall defect, allergic purpura, with the use of drugs like aspirin, penicillin, or corticosteroids, and in other diseases like uremia, cirrhosis, or leukemia.
• Prolonged clotting time with normal bleeding time can be seen in Hemophilia, Christmas disease, or any bleeding disorder in which clotting factors are deficient.
• Clotting time increases in Hereditary coagulation disorders like hemophilia and deficiency of factor XIII.
• Clotting time increases in Acquired coagulation disorders such as vitamin K deficiency, liver diseases, anticoagulant therapy.
• When blood comes in contact with the glass surface of a capillary tube it initiates intrinsic coagulation mechanisms.
• Activation of platelets causes release of phospholipids.
• High molecular weight kininogens and kallikerin convert factor XII to XIIa, which facilitates the intrinsic mechanism of clotting.
• Purpura is a condition characterized by capillary abnormality resulting in hemorrhages into the skin, mucous membrane, internal organs, and other tissues.
• Other tests to determine hemorrhagic disorders include prothrombin time, activated partial thromboplastin time, thrombin time, platelet count, and clot retraction time.
• In Hemophilia, clotting time is prolonged.
• In purpura, bleeding time is prolonged.
• In liver diseases, both bleeding time and clotting time are prolonged.