HEMA 2 LAB 3

• Activated Partial Thromboplastin Time (APTT) principle:

  • Calcium in whole blood is bound by sodium citrate anticoagulant to prevent coagulation
  • Plasma, after centrifugation, contains all intrinsic coagulation factors except calcium and platelets
  • Calcium, phospholipids substitute for platelets (partial thromboplastin), and an activator are added to the plasma
  • The time for the plasma to clot is the activated partial thromboplastin time
• Reagents and equipment needed for APTT test:

  • Water bath at 37°C
  • Calcium chloride 0.025 M
  • Partial thromboplastin containing an activator
  • Normal and abnormal control plasma
  • Test tube
  • Stopwatch
  • Ice bath
• Procedure for APTT test:

  1. Centrifuge specimen immediately after collection to obtain platelet-poor plasma

  2. Incubate a sufficient amount of 0.025 M calcium chloride at 37°C

  3. Pipet 0.2 mL of control plasma (or patient's plasma) into a test tube

  4. Pipet 0.2 mL of partial thromboplastin (containing activator) into the test tube with the plasma

  5. Mix contents quickly and place in a 37°C water bath for 5 minutes

  6. After 5 minutes, pipet 0.2 mL of prewarmed calcium chloride into the tube and start the stopwatch

  7. Mix the tube immediately after adding calcium chloride and tilt gently every 5 seconds

  8. After 20 seconds, remove the tube from the water bath, wipe it clean, and tilt it until a clot forms to stop timing

  9. Report patient results in seconds along with the normal test results determined by the laboratory