The Department provides a comprehensive consulting clinical and scientific service. The Duty Biochemist can be contacted by telephone on 0118 322 7704 (RBH) or 0300 6153444 (WPH) or via email on royalberkshire.biochemistry@nhs.net (RBH) or fph-tr.biochemistry.hwph@nhs.net (WPH) during normal working hours. Consultant (or deputy) advice is available on a 24-hour basis, and can be obtained out of normal hours through the hospital switchboard.
All analytical biochemistry procedures are maintained under a quality control system and subjected to additional technical validation when required, before the results are reported. This technical validation stage is intended to check the accuracy and precision of results.
Results exceeding determined ranges are then screened by one of the consultants or their approved senior colleagues and interpretative comments are added where appropriate. The clinical authorisation stage is intended for laboratory clinical staff to consider the results in the clinical context you describe on the request form. Relevant information such as medication, whether testing for diagnosis or monitoring known disease, day in menstrual cycle, etc is therefore essential.
The laboratory clinical staff may request additional biochemical tests that have a direct bearing on the case in order to maximise the service to you and your patient. Similarly, tests may be held back if they might be deemed misleading in the given circumstances or are not indicated from the information given or results already obtained. Such samples will be retained in the laboratory and may be still analysed after discussion with the duty biochemist.
Results are reported with a reference
range.
Please note that reference ranges are determined
statistically and includes 95% of the ‘normal’ population. This means
that 5% (or 1 in 20) of the ‘normal’ population will have a test result
outside the
reference range. There is more information on reference ranges and on
individual tests on the lab tests online
website
www.labtestsonline.org.uk/
.
Reference ranges can also be affected by age and gender. Ranges for female hormones are also affected by the timing within the menstrual cycle, for example progesterone should be taken in the luteal phase of the cycle, ideally seven days prior to expected menses.
Samples must be collected in to the correct sample tube using the correct order of draw and sent to the laboratory promptly. Incorrect sample collection and handling can produce artefactual results. The most common effects are listed below:
K-EDTA contamination of SST samples from an FBC tube:
When using the Vacutainer system always take the SST (Gold top) sample first. A small amount of contamination from the FBC Tube (Lavender top) will lead to artefactually raised potassium result and artefactually decreased calcium, magnesium & alakaline phosphatase results
Delay in sample separation:
Potassium starts to increase in unseparated samples after 6 hours storage at room temperature (15º C - 25º C). To enable the laboratory to spot this, always provide the time and date a sample is taken.
Sample storage in fridge:
At low temperatures (< 8º C) the ATPase Na-K pump becomes inactive, and there is a rapid leak of potassium out of the red blood cells in to the plasma. Depending on how the samples are transported and stored this effect can sometimes be seen on very cold days.
In vitro Haemolysis:
This can be due to difficult sample collection or the use of a small bore needle, or shaking a sample. Haemolysis releases cellular contents into plasma which most commonly causes increases in potassium, ALT and AST, lactate dehydrogenase and phosphate. Haemolysis may also cause interference with some analytical reactions such as urea and bilirubin. The laboratory will check for haemolysis before results are reported.
N.B. when using ward-based analysers specimens may be haemolysed but haemolysis cannot be seen in whole blood. This is a particular caveat when using blood gas analysers to estimate electrolytes.
Iatrogenic effects:
Iatrogenic effects include the effects of the drugs which may have been prescribed for the patient’s present illness as well as drip arm contamination in hospital patients.