pathology services handbook - St George's Healthcare NHS Trust

4.8 CREATININE CLEARANCE
For estimation of creatinine clearance, please ensure a blood sample is taken during the 24
hour urine collection period.
Urine samples should be taken to the laboratory as soon as possible after collection is
completed.
4.9 FAECES
Small faecal samples (‘walnut’ sized is approximately 10g) should be sent in blue plastic
screw-top container. After placing the sample in the container with the small plastic spoon,
clean the outside if necessary and place the container in a plastic bag. Please ensure that
these samples are properly labelled and are transported to the laboratory as soon as
possible. Time and date of collection MUST be indicated on all specimens to avoid rejection.
4.10 FLUIDS
Cerebrospinal fluid (CSF), preferably a clean tap, blood free sample, should be collected into
a plain silver top or white sterile container. CSF must be collected into a grey fluoride
oxalate tube for labile tests such as CSF glucose and lactate measurement. A minimum
volume of 0.5mL CSF (between 10-15 drops) is required for most investigations.
CSF samples for bilirubin analysis (xanthochromia) in suspected subarachnoid haemorrhage
must ideally be the last fraction taken, protected from light (e.g. foil wrapped around the
container) and NOT transported by pneumatic tube system to the laboratory. An information
sheet on collection of CSF samples for xanthochromia is available from Pathology Central
Reception (ext. 5468).
Other fluids (e.g. pleural fluid, amniotic fluid) should be collected into a monovette or silver
top container that is clearly marked with the fluid type. A volume of 5mL is sufficient for
analysis. Please contact the Duty Biochemist for further advice on the specimen
requirements and arrangements for the biochemical investigation of fluids.
4.11 LABILE TESTS
Specimens for labile tests require prompt handling and storage, and must be transported to
the laboratory as soon as possible. Please refer to table 4.23 – labile tests are indicated in
bold in the “Comments” column.
If you are not sure of the stability and collection requirements of the analyte you wish to
measure, please contact the Duty Biochemist on bleep 6032 for further information. For any
labile test you should always contact the laboratory ahead of sample collection to
enable prompt handling and storage of the specimen(s).
Please note that in some cases you may need to bring the specimen to the laboratory
yourself as the phlebotomy service, the pneumatic tube system or the portering services may
not be available. Any special collecting procedures are given in the specimen
requirement tables in Section 4.23. Please contact the laboratory (ext 5468) if ice is
required for transport.
4.12 TOXICOLOGY SCREENING
For suspected drug overdose, screening tests for a number of drugs may be appropriate.
Urine (8 mL) in a monovette, should be sent when the agent responsible for poisoning is
uncertain or unknown. Serum is not accepted for screening purposes, but may be
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