NHS Logo

*For most combinations of Biochemistry tests, one clotted (gold with gold insert clot activator and separation gel tube) sample is usually sufficient. This tube must be filled to the line.

Standard Profiles are made up of tests as follows:

Urea and Electrolytes (U&E)
Sodium, Potassium, Urea, and Creatinine (estimated GFR will be calculated on general practice and outpatient samples).  

AKI alerts are also generated for all U&E requests.

Liver Function Tests (LFT)
Total Protein, Albumin, Alkaline Phosphatase, Alanine Aminotransferase (ALT), Total Bilirubin.

Bone Profile
Calcium, Albumin, Adjusted Calcium, Alkaline Phosphatase

Lipid Profile
Cholesterol, Triglyceride, HDL, calculated LDL and Cholesterol/HDL ratio

Thyroid Function Tests
TSH only. If the TSH is outside set limits (>7 mU/L or <0.1 mU/L) then a free Thyroxine (FT4) will be automatically undertaken. FT4 on other samples and FT3 will be added if the clinical details and TSH/FT4 results warrant it. Full clinical details are essential for this algorithm to work. 

If you regularly request a certain group of tests to monitor certain patients we may be able to set up a special profile for you. Please contact Biochemistry to discuss.
 

The volume of serum obtained from a paediatric bottle is dependent on the PCV.  The department will endeavour to analyse as many tests as possible on the volume of serum available. Special tubes for the collection of paediatric blood samples are available. Biochemistry uses lithium heparin tubes for paediatric samples to ensure the maximum yield of plasma for analysis.

When requesting a U&E and glucose give priority to the lithium heparin paediatric tube as this can be used for glucose measurements if received within four hours.

All CSF samples should be collected into plain universal containers (white top, minimum of 1 ml in each) and one fluoride oxalate tube (about 0.5 ml CSF for glucose). These must be labelled with name, hospital number, ward, date of birth, the time that the CSF was obtained and sequence order of sampling. The last samples should usually be sent to Microbiology except when analysis for Xanthochromia is required.

When Xanthochromia analysis is required, the sample collected last should be sent to Biochemistry for analysis, a minimum of 0.5 ml is required and this sample must be protected from light and send to Biochemistry ASAP (but NOT in the air tube).

All other fluid samples, e.g. pleural, ascitic fluid should be collected into a plain sterile universal container (about 5 ml) and clearly labelled with fluid type.

Please indicate on the form what type of fluid is being sent as this will be printed on the final report together with the results. Please note that these are not UKAS accredited tests.

At least a two pence sized pellet of faeces on the spatula inside the stool container is sufficient for calprotectin and elastase and the sample must be transported straight to the laboratory. If Microbiology also required, please send a separate sample.

During working hours the requesting clinician can phone the Regional Toxicology Laboratory, 0121 507 4135 for advice on investigations and sample requirements. The laboratory will arrange transport to the Regional Toxicology Laboratory if required and can perform a urine screen for common drugs of abuse in Biochemistry.

Outside normal working hours the requesting clinician must telephone the West Midlands Poisons Unit on 0121 507 4007. If the request is accepted, the laboratory will arrange transport.

Some specialised tests may not be listed; please contact a Clinical Biochemist if you cannot find the test in the list of available assays.

The volumes given are as whole blood. In most instances a generous volume has been asked for to allow repeat determinations and/or further tests which may be indicated (or added on requests at a later date).  Samples are stored for at least 4 days after the collection date.  For this reason every effort should be made to supply the volume of blood requested.  It is appreciated that it is not always possible to provide these volumes, in which case the laboratory will do its best to perform the tests on the sample available.  If a very small volume is sent please indicate which tests should have priority. 

*One 5ml-clotted (gold with gold insert clot activator and separation gel tube) sample is usually sufficient for most combinations of Biochemistry and Immunology tests. Additional samples are usually only required for more specialist investigations.

The turnaround times for routine Biochemistry tests (e.g. U&E) from the time of receipt in the laboratory are:

More specialist work that is batched and tests that have to be sent away to other laboratories for analysis will take longer than this. Please see the specimen requirements tables on the next page which includes specific turnaround times for individual tests, including referred work.

Once results have been validated by the laboratory they should be available on the ward electronic reporting system immediately. Therefore telephone calls to the laboratory for results are unnecessary. 

The department stores primary sample tubes for about 4 working days.

Tests can be added to samples already processed by the laboratory where there is a clear indication that adding them to the original request would be of immediate clinical benefit, and there is no plan to re-bled patient.  Additional requests should be made within 24h of the original sample collection where possible.  If the original sample is haemolysed no additional tests can be added.

Add-on requesting is limited to Acute Investigations:

Please consider requesting the following tests when the patient is next bled if results would not be of immediate clinical benefit: B12/Folate/Ferritin, TSH, and Tumour Markers.
For requests that fall outside this repertoire (including Immunology tests) please call the Duty Biochemist to discuss.

Requests for add-ons MUST be received on a new request form, which should be sent to lab ideally with the request number of the original sample in the clinical details. This is to ensure add on tests are send back to the consultant who requested them, and to also minimise phone calls to the laboratory.

Please also ensure the laboratory has the correct sample type for the add-on or it is not a test that requires urgent processing, or we will not be able to process.

Haemolysis, icteric and lipemic indices are measured on all Biochemistry samples and tests results are not reported when the indices are above the accepted reportable cut off where there is likely to be significant interference for that test

EDTA contamination (e.g. from FBC tube): Potassium will be increased,     Calcium, magnesium and ALP decreased.

Prolonged delay in centrifugation of sample: Potassium, phosphate, LDH will be increased, and bicarbonate decreased.

Inappropriate sampling site, e.g. sample taken from a drip arm: Increase in drip analyte (e.g. sodium or glucose). Dilutional effect likely to be seen on other analytes.

Potential for Biotin interference in Immunoassays

The use of over-the-counter (OTC) high dose biotin (Vitamin B7) supplements has gained popularity in recent times. Many patients take biotin supplements (generally 5-10 mg tablets) marketed as beauty products to improve the health of hair, skin and nails. High-dose biotin (100 mg) is sometimes prescribed to treat metabolic diseases and there are also ongoing trials of mega-dose (up to 300mg/d) Biotin in Multiple Sclerosis. The Biotin – Streptavidin couple is part of the assay design for many biomarker immunoassays. If patients are taking large doses of this Biotin / Vitamin B7, there is known potential for significant interference in immunoassays for a number of commonly requested tests in Biochemistry.
Interference may be positive or negative depending on assay design: sandwich-type immunoassays are generally negatively affected, and competitive designs are usually positively affected. 

If you have a test result that does not fit with the clinical picture, it is worthwhile excluding biotin ingestion as a potential cause of test interference, by asking the patient / parent / carer about any OTC supplements or checking for a biotin prescription. 
Clinicians caring for patients being investigated for chest pain / acute coronary syndrome should take particular care when interpreting Troponin I results where biotin can cause a negative interference and potentially falsely reassuring results. In such cases, the clinician should ask about biotin supplements for all patients for which a Troponin I is requested.

Please contact the Duty Biochemist if you wish to discuss any results where interference is suspected.