A coagulation screen consists of the prothrombin time (PT) and activated partial thromboplastin time (aPTT). If a fibrinogen assay is required please request a Clauss fibrinogen separately. Note that the derived fibrinogen should not be used for clinical decision making, and we are currently working to phase out reporting derived fibrinogen.
If you require an INR to monitor warfarin please request an INR and not a coagulation screen.
If you require an aPTT ratio to monitor unfractionated heparin please request an aPTT ratio (aPTT for heparin) and not a coagulation screen.
Tube
05 (CP) – Citrate
ID
Tests&Tubes0034
Additional Information
The prothrombin time is considered stable for 24 hours. Samples older than 24 hours will be rejected.
The stability of the aPTT with respect to time is less clear. Based on the results of local validation the haematology blood sciences laboratory will only reject samples older than 24 hours at the point of analysis. Users need to be aware, however, that the risk of a spuriously prolonged aPTT may increase when the sample is more than 4 hours old. This can pose problems in primary care as there may be delays in samples reaching the laboratory. GPs should consider asking patients to attend a hospital phlebotomy room if an aPTT is required.
More stringent time requirements are in operation in the specialist coagulation laboratory with respect to aPTT.
When an aPTT is performed for the purpose of monitoring unfractionated heparin, the sample must be analysed within one hour of phlebotomy.
Send to
Blood Sciences Cross Site
Contact
For further details please contact Leeds Pathology customer services: [email protected].
Collection Con
Citrate tube must be filled to the fill line.
Instructions for Lab Staff: Standard lab processing- No special requirements.
Sample REQ
Blood.
Ref. Range Notes
Blood Sciences Reference ranges available through the useful information and links page:https://www.leedsth.nhs.uk/a-z-of-services/pathology/blood-sciences/useful-information-and-links/
IP Acute TAT
1 Hour
IP Routine TAT
6 Hours
GP TAT
24 Hours