In this section
Sample types and reference ranges are shown in the Biochemistry test information.
Blood samples
Avoid contamination – When taking a series of blood specimens, it essential that the serum sample is taken first, followed by lithium heparin samples then the fluoride samples and any EDTA tubes last of all. Failure to adhere to this sequence will lead to contamination of blood samples with anticoagulants/preservatives. This contamination produces spurious and invalid results.
Avoid haemolysis, drip contamination, adverse temperatures (over 30°C or less than 10°C, unless otherwise stated) and prolonged venous constriction.
Ensure thorough and instant mixing of blood with anticoagulant (heparin, fluoride EDTA or potassium EDTA) for plasma samples.
Do not transfer blood from one tube to another e.g. EDTA to Lithium Heparin.
Do not leave Clinical Biochemistry blood samples in the fridge (4°C) or overnight at room temperature. If in doubt, please contact the laboratory for advice.
Leaking blood tubes will be discarded.
Urine samples
Most of the urine assays are normally reported as a 24 hour output, and a full 24 hour collection is required. Please ensure that start and end dates and times are noted on the bottle label.
Random samples or overnight collections are adequate for some tests and these are indicated in the table.
Some analyses require a specific preservative in the collection bottle – check before starting collection. Special bottles are held by the Biochemistry Department and can be collected from there or the reception area in the Clinical Sciences Centre by the portering service or ward staff.
Please complete the bottle label as well as the request form.
Creatinine clearances can only be calculated if the blood creatinine is measured within 24 hours of the 24 hour urine.
Pleural fluid samples
For health and safety reasons, pleural fluid MUST be collected into the tube detailed on the HIVE system or they will not be analysed. For most samples, the white top serum tube is required:
Universal containers are not acceptable. Yellow top fluoride EDTA tubes are required for pleural fluid glucose, whilst samples for fluid pH should be collected into blood gas syringes.
A simultaneous blood sample for general biochemistry into a tube and glucose into a fluoride tube will be helpful for interpretation. See Light’s criteria for evaluating pleural fluid.
Sample volumes
The HIVE/ICE systems will calculate the number of blood tubes required for the tests you request and will print out the required number of barcodes. Please ensure the correct barcode is attached to each tube, and do not attach more than one barcode to a single tube.
(Last reviewed August 2024)