Collecting Pathological Samples

Blood samples

When collecting blood samples, fill tubes containing anticoagulant to the fill line and mix gently immediately after collection. Vacutainers can be used for large animal blood sample collection, and a needle and syringe for small animals. The jugular vein is the preferred collection site using a wide bore needle to prevent haemolysis of the blood from using excessive suction during collection. The cephalic and saphenous veins are alternative venipuncture sites. Ensure the venipuncture site is clean and swabbed, wear gloves and ensure you have adequate restraint prior to collecting a blood sample.

Always label your sample tubes with permanent marker immediately with the animal's details and the date and time of collection. Serum samples can be processed by allowing the blood to clot in an upright position and removing the serum from the tube prior to sending the sample for analysis to avoid haemolysis (bursting of the red blood cells into the serum) during transit. A more ideal method of serum separation is to centrifuge the sample -balance the centrifuge by adding a tube filled with the same volume of fluid in the opposite well in the centrifuge for safety.

The following table is a guide to the sample type required for some specific laboratory tests - seek guidance from your processing laboratory for confirmation of sample requirements, which can vary depending on the equipment used to analyse the sample.

Test Required	Sample Required	Comments
Haematology	EDTA	Mix gently immediately after collection
Biochemistry	Serum	Centrifuge after permitting sufficient clotting time (min 2 hours)
Fibrinogen	Citrate	Mix gently immediately after collection
SAA	Serum	Needs to be processed quickly as the half life is very short
Electrolytes	Heparin	Mix gently immediately after collection
Glucose	Fluoride oxalate	Can use fresh whole blood if tested immediately
Insulin	Serum	Fasting sample required
Prothrombin clotting time	Citrate	A normal sample is required for comparison
Progesterone	Serum
Oestrone Sulphate	Serum
Testosterone	Serum	Request Testosterone before Inhibin for GCTs
IgG	Serum	Measurement techniques vary so check sample requirements
ACTH	EDTA plasma	Freeze plasma as soon after collection as poss (max 2 hours)
Selenium	Heparin/Serum	Send Heparin for deficiency testing, serum for toxicity testing.
Zinc	Serum	Avoid using tubes with a rubber bung
Drugs testing	Serum or Heparin	Send to HFL
Virus Titres e.g. EHV	Serum	Take 2 samples 14 days apart (freeze 1st)
Tapeworm ELISA	Serum
Fractional Excretion test	Serum and urine	Collect both samples simultaneously if possible and do not permit food or fluids until both are collected

Sending Samples by Post

There are some absolute requirements for sending samples through the UK postal system. Blood samples cannot be posted outside the UK without an export license - use a large lab to send your sample as they will have the required licensing.

Packaging samples should follow the guidelines required by Royal Mail, namely:

• The maximum weight or volume permitted in any one package of diagnostic specimens is 50g/50ml. Samples that exceed this limit need to be packaged into several smaller packages rather than one large one.
• Use leak proof containers – seal the lid with a little parafilm or tape to ensure this. Label the sample accurately and in permanent ink including the sample type (e.g. blood, urine etc). Make sure samples preserved in Formalin are marked as such (in case of breakage during transport).
• Package the sample with sufficient tissue paper or cotton wool to absorb the entire contents of the sample should there be a leak whilst in transit. Always package bloods tubes/containers individually so they are kept separate from one another.
• Seal your wrapped sample in a separate outer packaging that is leak proof such as a sealable plastic bag.
• Place the sample and the lab request form into an envelope or jiffy bag that is clearly labeled in permanent ink ‘Diagnostic Specimen’.
• It is advisable (but not required) to add a returns address so that the practice can be contacted in the event of any problems.