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Specimen Collection

 

2.7 mL Citrate Venous Blood

or

1.8 mL Citrate Venous Blood

or

  1mL Paediatric Mini-Citrate Venous Blood

• Tube must be adequately filled

Reference Intervals

Age	Triniclot RI	Actin RI
Birth - 1 day	39 - 51	39-47
2 - 5 days	36 - 54	37-50
6 - 30 days	35 - 50	35-46
31 - 90 days	32 - 46	32-43
3 - 6 months	33 - 41	33-38
6 months -  1 year	32 - 49	32-45
1 year - Adult	25 - 38	24-35

 

Uncertainty of Measurement: 4%

Therapeutic - Units: seconds

Age Range	Either Sex
All	50 - 85[1]

[1] Triniclot APTT Therapeutic Range for unfractionated heparin.

Therapeutic range based on CLSI Guidelines H47 A2 (2008) correlates to 0.3 - 0.7 IU/ml.
Turnaround Time: Within 2 hours
Assay Method

At LabPlus APTT screening will now be offered using both Lupus sensitive (Triniclot HS) and Lupus insensitive reagent (Actin FS). Further information regarding sensitivities of these reagents are available on request.

Method effective from 28/07/2022.

Diagnostic Use and Interpretation

The APTT is a useful and sensitive test to screen for deficiencies/abnormalities of the intrinsic and common pathways of coagulation cascade and for monitoring of heparin therapy.

If APTT is prolonged and the cause is not due to heparin contamination or other pre-analytical problems, correction studies with normal plasma and testing with alternate APTT reagents may be required:

• complete correction suggests factor deficiency
• no or partial correction suggests heparin, lupus anticoagulant or presence of factor inhibitor (antibody)
• addition of protamine sulphate corrects heparin defect
  

Requesting physician will be contacted if more complex and expensive testing is indicated.

Limitations of Procedure:

APTT may not detect mildly reduced coagulation factor levels of 30 - 50%. If mild haemophilia is suspected, even in the presence of a normal APTT, specific factor assays should be performed.

Collection artifacts such as heparin contamination, clots, incompletely filled tubes (excess citrate),  polycythemia (citrate/plasma ratio inappropriate), high lipid levels, TPN may spuriously prolong APTT.

Interpretation:

APTT results are often interpreted with results of the PR in determining which condition may be present.

Causes of prolonged APTT include:

Haemophilia A (factor VIII deficiency), haemophilia B (Christmas disease, factor IX deficiency), von Willebrand Disease, factor XII deficiency (not usually associated with abnormal bleeding), factor XI deficiency, liver disease, disseminated intravascular coagulation, heparin therapy, factor inhibitors (most commonly against F VIII), lupus anticoagulant.

Short APTT usually reflects factor activation from difficult collect or recent trauma/surgery.

See:

Coagulation Factors

Heparin Therapy Control

Lupus Anticoagulant

Contact Information

For further information contact the Haematology laboratory (Ext 22067) or:

Dr Nicola Eaddy		Ext 22071
Dr Peter Bradbeer		Ext 22062
Dr Anna Ruskova		Ext 22137

Last updated at 15:21:03 14/11/2023