Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
There are some mutations in the Factor VIII molecule which change its behaviour in the standard APTT based 1 stage Factor VIII assay. The mutations will typically lead to an overestimation of the Factor VIII activity in plasma by up to seven fold – the patient has a more severe bleeding diathesis than that suggested by the 1 stage Factor VIII result. The chromogenic assay is used to investigate and monitor these patients. There is also a mutation which gives a low result in the 1 stage assay but a considerably higher result in the chromogenic assay, again the bleeding symptoms are consistent with the chromogenic result. The assay is referred to as either a 2 stage assay or chromogenic assay as the procedure mimics the 2 stage assay with the generation of Xa
Specimen container paediatric:
Light blue – sodium citrate
Specimen container adult:
Light blue – sodium citrate
Minimum volume paediatric:
1.3ml
Minimum volume adult:
2.7ml
Special requirements:
Tube must be correctly filled to line, to ensure correct ratio of blood to anticoagulant, ensure adequate mixing.
Sample stability:
4 hrs
Transport requirements:
Sample must be transported to lab without delay (see sample stability information)
Freq analysis:
As required or weekly
Add on test:
[email protected] (external)
Quality assurance:
UK NEQAS Blood Coagulation
Reference ranges:
50 – 150IU/dL