This website is part of Barnsley Hospital NHS Foundation Trust - view our homepage.

Adding tests to existing requests

The Blood Sciences department receives in excess of 5000 samples per day. The storage of these samples must therefore be limited to a maximum of 4 days.

Sample viability

The department does not recommend or encourage the use of ‘add-on tests’ but under specific circumstances tests may be added as shown below.

For tests not routinely performed within the Blood Sciences department refer to the specific analytes within the test repertoire table.

Routine chemistry, endocrine and therapeutic drug monitoring 

These samples are mostly, stable for up to 2 days.

With the exception of:

  • serum glucose – stable for up to 4 hours
  • urea and electrolytes –  stable for up to 24 hours
  • troponin I – stable for up to 24 hours
  • creatine kinase (CK) – stable for up to 24 hours
  • Ca125 – stable for up to 24 hours
  • BNP – unable to add onto existing requests

Routine haematology

Stable for up to 24 hours from venepuncture. Please note that for blood films, integrity may be affected. This depends on pre-analytical storage and when an add on request is received. Morphological features may be better interpreted on a fresh sample.


Stable for up to 8 hours from venepuncture (this includes requests for D-dimers).

With the exception of:

  • referral coagulation assays, such as - thrombophilia, lupus, factor assays.

These tests cannot be added onto an existing sample. Fresh samples are required for processing. If in doubt, please contact the laboratory prior to sending the add on request.