APTT.pptx

Avtivated partial thromboplastin time

1. Activated partial thromboplastin time (APTT)

2. Specimen:- Citrated plasma Principle:- Partial thromboplastin (brain extract in chloroform) is incubated with Kaolin (factor XII contact factor activator). The clotting time of plasma is determined after the addition of calcium ions.

3. Requirements:- Water bath (37°C) Test tubes Stop-watch Partial thromboplastin (brain extract in chloroform) Calcium chloride (0.025 mol/L) Kaolin reagent: 2.0 gm/dl in normal saline Normal plasma (control)

4. Procedure:- Pipette 0.1 ml of brain extract, 0.1 ml of kaolin reagent and 0.1 ml of plasma in a test tube. Incubate at 37°C for one minute. Add 0.1 ml of calcium chloride and start the stop watch. After 20 seconds, observe the formation of the clot by tilting the test tube. As soon as the clot forms, note the time.

5. 5. Repeat the procedure by using a normal control plasma. Normal range:- 30-40 seconds

6. Clinical significance:- Prolonged APTT is found in:- Administration of Heparin Liver disease Vitamin K dificiency Kidney disease Patients suffering from Haemophilia A, Haemophilia B. DIC (Disseminated intravascular coagulation) 7. Congenital deficiency of factors VIII, IX, XI and XIII.

7. Sources of error:- Faulty collection of blood. Excess anticoagulant or insufficient anticoagulant. Reagent not good. Glass tubes are not clean. Incorrect temperature of water bath. If temperature is increased, factors may be destroyed.