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Laboratory Medicine

General Information / Add On Requests

If additional tests are required on a sample already received in the laboratory, we require evidence that a responsible clinician has authorised the additional test(s). This can be via an additional paper request form or the electronic equivalent.

Biochemistry York & Scarborough Sites

Routine Biochemistry blood samples are archived and kept for a minimum of three days. Beyond this, add-on test requests cannot be processed. 

Please note that some analytes are labile and deteriorate rapidly and some tests are not suitable for requesting as ‘add-ons’.  In these cases an add-on cannot be processed and a fresh sample will have to be taken.  Most routine Biochemistry tests are stable for 3 days. Exceptions are:

 No add-ons can be accepted for the following tests:

            Bicarbonate, Glucose, Ammonia, Lactate and HCG

 Test with 24 hour stability:

            Troponin T, D-Dimer, B12, Phosphate, Total Bilirubin, PSA

 Tests with 48 hour stability:

            Folate, Ferritin, CK, Osmolality, Direct Bilirubin

To request an add-on test:


  • Add-on tests should be requested via CPD
  • For instructions on how to request an add-on via CPD please Click Here
  • For tests that cannot be added on via CPD or if the request is urgent please phone:
    • York: (01904 72) 6802 option 1
    • SGH: (01723 34) 2351

 GP and external locations

  • Non-urgent add-on requests can be made via email using the electronic add-on request form: Click Here
  • Add-on requests can be made by phone:
    • York: (01904 72) 6802 option 1
    • SGH: (01723 34) 2351

 The Blood Sciences add-on policy

Details of Blood Sciences initiated add-on testing can be viewed by Clicking here

Details of the Clinical Biochemistry Add-on policy can be viewed by Clicking here


Haematology York Site

Additional examinations may be requested up to 24hrs for coagulation samples and up to 3 days for haematology samples, however requests for blood films, malaria parasite screening and ESR testing are best performed on fresh samples that are <24hrs old.  If you want to add further tests to a sample please ring (01904 72) 6802 option 1.

Haematology Scarborough Site

This procedure is designed to aid the additional analysis on haematology blood samples to ensure a full audit trail and conform with the principles of clinical governance. It is not for use with add-on test requests for urine and faecal analysis. All requests for additional tests must be accompanied by a signed request form clearly stating the tests required. This form is then used to generate further analysis. Haematology: D-Dimer and Paul Bunnell tests are only viable for 24 hours while Plasma Viscosity can be added after a maximum of 5 days.

Microbiology York & Scarborough Sites

Blood samples for serology are kept for 3 weeks, antenatal samples for 1 years. Needlestick samples are kept indefinitely. We also keep a small number of acute serum samples until a convalescent sample is received. If you want to add further tests to a blood sample we will require an additional request. Please phone 01904 726301 to make arrangements.

Most other samples are kept for at least 1 week before they are discarded.  Some samples are kept longer depending on the tests requested. If you want to add further tests to a sample please ring 01904 725721 (York) or 01723 342288 (Scarborough). We will check if we still have the sample and then add the tests. Please note that in some cases the sample may be unsuitable and we will ask you to obtain a fresh sample.

Web Page updated 24: 21/10/20

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