Therapeutic ratio range 1.8 - 3.3 times normal control

Sample Requirements
The sample must be received within the laboratory within 4 hours of collection. The samples must be correctly filled as the ratio of anticoagulant to blood is crucial for accurate tests results. If the sample cannot reach the laboratory within 4 hours the sample must be centrifuged (3000g for 10 minutes) and separated and frozen

The APTT is used in conjunction with the APTT to form a clotting screen

Prior to 01/07/2010 the reference range was 23.0 - 35.0 secs.