Specimen requirements and reference ranges
Specimen requirements and reference ranges are shown in this table.
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
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
Do not leave Clinical Biochemistry blood samples in the fridge
(4°C) or overnight at room temperature. If in doubt, please contact
the laboratory (Duty Biochemist bleep 4375) for advice.
Leaking blood tubes will be discarded.
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
Random samples or overnight collections are adequate for some
tests and these are marked 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 general biochemistry collect into a fluoride tube, glucose
into a fluoride oxalate and sample for acid base assessment
collected into a blood gas syringe and treated as a blood gas
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.
One fully filled tube will generally contain sufficient blood
for analysis of all profiles listed above. However this does depend
on the MCV of the patient and assumes that a minimum of 2mls of
serum or plasma is able to be separated.
For single analytes 1ml of whole blood is usually
For all assays not quoted above please send one full tube of the
correct type, if collection of multiple tubes causes a problem
please call the duty biochemist for advice.