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Coagulation sample collection

For all coagulation tests three citrate tubes will be the maximum requirement (although other sample types may be required) – please see test directory for specific tests. For difficult to bleed patients and paediatric patients 1ml citrate sample tubes are available.

Please ensure that there is no possibility of contamination of sample with heparin or other IV fluids - eg. flushed from venflons etc.

Please collect coagulation samples before all other sample types with a minimum of stasis or delay. Do not top up coagulation tubes from other samples.

Please ensure each tube is correctly filled – under or over-filled samples give unreliable results and will not be tested.

All coagulation samples must be received and assayed within six hours of collection.

Suggest discuss with a consultant haematologist before requesting any of the following investigations:

·         Investigation of a possible bleeding disorder

·         Investigation of a possible thrombophilia

Please state any current anticoagulation therapy on the request form.

Click here for Commonly asked Questions and Answers about Thrombosis

General guidance for interpretation of Routine coagulation tests

Raised INR

Patient taking oral anticoagulants

Consider acquired coagulation disorder e.g. Liver disease, DIC

Consider hereditary coagulation disorder (rare)

Raised APTT ratio

Patient on unfractioned heparin

Consider Acquired coagulation disorder e.g. Liver Disease, DIC

Consider Hereditary coagulation disorder e.g. haemophilia (FVIII deficiency), Christmas disease (FIX deficiency), vWD, Lupus inhibitor

D-Dimer advice

D-Dimer is a useful diagnostic test as a negative predictor for deep vein thrombosis (DVT) and pulmonary embolus (PE). It can be used when these conditions are suspected to prevent unnecessary anticoagulant therapy and invasive diagnostic tests.

The D-Dimer should only be used when the pre-test probability score (Wells score) is low.

However, many clinical states are associated with an elevated D-Dimer level and so in the following situations the D-Dimer is of no value:

  • Pregnancy
  • Post-natal
  • Post-operative
  • Post-trauma
  • Myocardial infarction
  • Peripheral arterial disease
  • Thrombolytic therapy
  • Malignancy including leukaemia
  • Sickle cell crisis
  • Newborn infants
  • Liver and renal disease
  • Gram-negative bacteraemia

Anticoagulant therapy has the effect of changing the D-Dimer level and so tests should not be performed on patients receiving either heparin or warfarin.

Page last updated: 29/10/21
Next review date: 29/10/23

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