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Labile (unstable) tests and Urgent samples Many tests can be performed urgently but these must be discussed with the laboratory in advance. Clinicians are advised to inform the laboratory prior to submitting samples for ammonia and lactate assay to ensure instrumentation is available to enable rapid analysis. Similarly, a number of Chemical Pathology investigations have special requirements for collection or must otherwise be brought directly to the laboratory for immediate processing, these are summarised (below): -

Test

Sample requirement(s)

ACTH

Collect into EDTA, rush to lab. Separate within 30mins.

Aldosterone: Renin

Collect into Lithium Heparin, rush to lab. Separate within 30mins. Note recumbency, medication and electrolytes on request.

Amino Acids (Plasma)

Collect into Lithium Heparin, rush to lab. Separate within 30mins.

Ammonia

Collect into Lithium Heparin, rush to lab. Separate within 30mins. Provide spare (empty) heparin tube for blanking purposes.

Arterial/ Venous Blood Gases

Collect into Lithium Heparin syringe, expel air and mix thoroughly. Eject a few drops to gauze to remove clots. Rush to lab and process within 15mins.

Calcitonin

Collect into clotted serum tube. Rush to lab. Separate within 30mins.

Cryoglobulins

Collect into clotted serum tube. Rush to lab and transfer to incubator - maintain at 37°C throughout (flask, armpit etc.)

CSF Oligoclonal Bands

Collect CSF and blood into clotted serum tube simultaneously, submit together.

CSF Xanthachromia

Collect CSF and blood into clotted serum tube simultaneously, submit together. Protect from sunlight - refer to specific guidance.

Gastrin/ Gut Hormones

Obtain Aprotinin-containing Heparin tubes from Biochemistry lab. Rush to lab on ice. Ensure patient fasted and note relevant medication on request.

Homocysteine

Collect into Lithium Heparin, rush to lab. Separate within 15mins.

Insulin/ C-Peptide

Collect into clotted serum tube. Rush to lab. Separate within 30mins.

Lactate

Collect into Fluoride Oxalate. Rush to lab and analyse within 20mins.

Organic acids (Urine)

Rush to lab. Freeze within 1hr of collection.

Porphyria screening

Refer to porphyria protocol for appropriate sampling guidance. Protect all samples from sunlight.

Reducing substances

Rush to lab and analyse within 1hr of collection.

Very Long Chain Fatty Acids

Collect into Lithium Heparin, rush to lab. Separate within 30mins.

White Cell Enzymes

Collect 5mL blood into lithium heparin, rush to lab early in working day/ week (samples must be analysed within 24hrs.)

For a comprehensive breakdown of sample requirements, referral centre details and turnaround times please refer to the Biochemistry test directory.

Last updated: 25 June 2015