PTD - 52

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Test Directory -  APTT 50/50 Correction


APT 50/50

Clinical Indications

Follow up test to investigate cause of unexplained prolonged APTT. Differentiates between possibility of factor deficiency or acquired coagulation inhibitors

Request Form 

Combined Pathology Blood form (Yellow/Black or Blue for GP's)


On Request also part of Lupus anticoagulant screen

Specific Criteria

  DO NOT use heparinised syringes / lines for collecting coagulation screens. Patient should be bled with minimal stasis, and samples received in lab within 2 hours of collection.

Turnaround Time

Within 2 hours of reaching the laboratory (If part of Lupus screen: 28 days)


 Citrated whole blood




  1 x Blue capped vacutainer tubes


  Samples must be received by lab within 2 hours of collection.

Lab. Handling

Lupus screen: Sample is double spun, the plasma aliquoted and then frozen

Causes for Rejection

Inadequately labelled, unlabelled, haemolysed, under-filled, clotted  or lipaemic samples.


  Activated sample, sample haemolysis or lipaemia..

Reference Range

  APTT 50/50: 21 - 32 seconds


Correction of prolonged APTT : Suggestive of Factor deficiancy No correction of APTT (to within 3 - 4 seconds): Suggestive of inhibitor

Version 1.0 / January 2013