The activated partial thromboplastin time (aPTT) assays the intrinsic and common pathways of the coagulation cascade. The aPTT ratio, which is used to monitor unfractionated heparin, is calculated from the aPTT.
If you wish to monitor unfractionated heparin please use the ‘aPTT (for heparin)’ request.
If the patient’s haemostatic function needs to be assayed eg in the setting of active bleeding, please request a coagulation screen and Clauss fibrinogen.
Tube
Coagulation Tube (Blue)
05 (CP) – Citrate
ID
12614
Availability
Daily 24/7
Additional Information
When an aPTT is performed for the purpose of monitoring unfractionated heparin, the sample must be analysed within one hour of phlebotomy.
The stability of the aPTT with respect to time in other situations is a matter of debate. 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.
Turnaround Time
A&E and monitoring unfractionated heparin: 1 hour
Day Case: 6 Hours
In-Patient: 6 Hours
Out-Patient: 24 Hours
GP: 24 Hours
Sent To
Blood Sciences Cross Site
Contact
For further details please contact Leeds Pathology customer services: [email protected].
Collection Con
1 x Citrate tube must be filled to the fill line please.
Instructions for Lab Staff: Standard lab processing- No special requirements.
Sample Type
Blood
Sample Storage
Room Temperature.