Clotting Screen

Department of Haematology

Notes

• Blood samples should ideally reach the laboratory within 2 hours. Samples greater than 24 hours old will not be tested.
  
• Coagulation tests must be performed on samples taken by clean venesection, and filled to the appropriate level (in line with black arrow).
  
• Overfilled, underfilled and haemolysed samples will give erroneous results and will not be processed.
  
• Samples should not be taken from indwelling lines that have been flushed with Heparin as contamination frequently occurs despite the initial draw.
• A clotting screen is not a suitable test request to monitor patients on unfractionated, fractionated heparin (APTT ratio) or on Warfarin (INR).
  
• Test performed at GRH and CGH.
  

Investigation of possible bleeding disorders

The most important indicator of bleeding risk is the patient history

If a bleeding disorder is clinically suspected the initial tests should include a full blood count and coagulation screen. This will detect the vast majority of acquired bleeding disorders and most severe hereditary disorders. A few disorders, notably von Willebrand's disease, cannot be excluded by these tests alone.

If the coagulation screen is abnormal, or there is a strong history of abnormal bleeding episodes despite a normal coagulation screen, the laboratory or a consultant Haematologist should be contacted for advice about further investigation.

A coagulation screen includes the following tests:

• Prothrombin Time (PT)
  
• Activated Partial Thromboplastin Time (APTT)
  
• Fibrinogen
  

GHNHSFT Guidelines on Performance of a Coagulation Screen

In accordance with the Trust policy, a Coagulation Screen will only be performed in the following instances:

• Investigation of a patient with a significant history of bleeding or bruising
  
• Monitoring coagulopathy associated with massive transfusion.
  
• As part of an investigation into Disseminated Intravascular Coagulation (DIC)
  
• In patients with liver or gall bladder disease
  
• In patients with Systemic Lupus Erythematosis (SLE)
  
• In cases of Intra-Uterine Death (IUD)
  
• Patients having liver or renal biopsies, Endoscopic Retrograde Cholangio-Pancreatography (ERCP), insertion of central venous lines, or insertion of permanent pacemakers.
  
• For baseline screening prior to starting anticoagulation
  
• Patients on intensive care and high dependancy units (DCC, ITU and HDU)
  
• in patients with pre-eclampsic toxaemia (PET)
  
• In patients with Cystic Fibrosis
  
• In oncology patients with thrombocytopenia
  
• In drug overdoses
  
• In patients due to undergo radiological procedures
  
• In patients <12 years old
  

Please clearly state the reason for the request on the request form. Requests for clotting screens that do not fulfill the above criteria, or where there are insufficient / no clinical details provided, will not be performed

Sample Requirements

3.5ml, 3ml or 2ml Trisodium Citrate tube.

Patients with a Haematocrit of >0.55

Patients with high haematocrits, including neonates, may require a modified Trisodium citrate tube. Please phone the Department of Haematology on ext 5242 (GRH) or ext 4058 (CGH) to discuss the availability of modified tubes on these patients. The modified tubes will be sent directly to the ward and must only be used for the patient specified.

Turnaround Time

• Clinical emergency: 30mins
  
• Other urgent samples: 60 mins
  
• Routine: within 2 hours
  

Reference Ranges