Reference ranges are supplied strictly for guidance only, and
these should be used rather than those quoted in textbooks,
diaries, etc, as both methods and units vary from department to
These should not be published as methodology changes in line
with the introduction of new techniques the ranges become outdated
and therefore are subject to constant review.
The current reference/therapeutic range is always included with
the final report. 5% of the healthy population will have results
marginally outside the quoted reference range. Ranges may be
affected by age, gender, ethnic group, pregnancy, time of sampling
and many other factors. Detailed information or advice on
interpretation is always available from the laboratory.
Validity of results
Results are automatically validated if they are within preset
ranges and have no error flags from the instruments, eg,
Haemolysis, Lipaemia and Icterus. Ranges have been discussed and
approved by senior scientists and consultant staff.
Results outside these ranges are scrutinised by qualified staff
and authorised HCPC registered Biomedical Scientists or the duty
Biochemist/Medic or Consultant. Comments may be appended and
additional analyses undertaken based on the clinical details
provided and on previous results.
Whilst internal and external quality assurance programmes are in
operation to ensure accuracy and precision of results, occasionally
random errors may occur and escape detection.
The clinician is often best placed to detect such errors.
Therefore if you doubt the validity of a result, it is vital that
you contact the relevant 'Advice/Interpretation' extension at once
so that we can investigate and re-test samples whenever
Please remember that certain factors may affect and possibly
invalidate some test results, causing potential biological and
Examples include blood transfusion and other intravenous fluids,
antibiotics, anticoagulants, drugs, timing of specimen in relation
to drug dose, time of day, fasting status, type of tube.
A common problem which may affect the reliability of results is
a delay in transport to the lab, especially if it is critical that
the sample is received on ice or within a specific time limit. This
is described in the table of tests if relevant to a particular
It is important to remember to supply details of drug dose and
timing, as prompted in ICE, or on a handwritten request.
In order to maintain sample viability there is a requirement for
samples to arrive within the target times outlined.
For the routine Biochemistry blood profile tests, blood glucose
and HbA1c and endocrine tests that are collected in primary care
the target time from venepuncture to delivery in the laboratory is
four hours with a maximum of six hours.
This includes samples for PTH collected into EDTA tubes. A small
number of specialised tests must be delivered to the laboratory in
under this time and/or be transported on ice as indicated. These
tests are not ones that would normally be collected in primary
Advice on these specialised tests is provided on a test by test
basis by the departmental duty biochemist (0161 276 1234 bleep