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APTR (Activated Partial Thromboplastin Time Ratio)

Blood Sciences Test


Sodium citrate

Minimum sample volume

As with all coagulation tests the tubes must not be underfilled – fill to the line on the tube.

Factors affecting results

Haemolysis should be avoided by:

  • Mixing the tube by inversion
  • Do not shake

Delay in sample analysis –┬áSamples should be tested the same day

Reference Range

Non anticoagulated Adult 0.87 – 1.13

For unfractionated heparin therapy 1.5 – 2.5

The result is given as a ratio of the patient test time/ mean normal control time

Test Usage

APTR is not suitable for monitoring low molecular weight heparin. See Heparin Assay

Diagnosis of coagulopathy/Unfractionated Heparin monitoring/Detection of Lupus anticoagulants


In house

STAT availability


Turn around time

1 hr – STAT samples

4 hr – routine samples

Clinical Advice

Clinical advice is available from the Haematology Medical team (contact RD&E switchboard on 01392 411611)

Specimen Labelling Procedure
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