Blood Sample Handling

Syringe Needle Size for Blood Collection

Before collecting a blood sample choose the right syringe needle size. The needle gauge will vary based on patient size. Use the needle with the largest bore governed by the size of the vein, to minimise the possibility of haemolysis. Be especially careful with ill animals, because they may have fragile erythrocytes.

Small Species (Adult weight up to 30kg) – 22G

Medium Species (Adult weight 30-60kg) – 20G

Large Species (Adult Weight above 60kg) – 18G


Collection Tubes

After you have collected blood with a syringe, choose the appropriate tubes for each type of diagnostic testing that will be performed. There are more than 9 types of tubes used for blood collection. They contain the appropriate anticoagulant indicated by their stopper colour.

Sodium Citrate- Coagulation, Fibrinogen

Serum (Clot Activator) – Harvesting of serum for common biochemical determinations

Lithium Heparin – Plasma for Biochemistry

EDTA – Haematology preserves cell volume and morphology.


Transfer the Sample

After you have collected the blood with a syringe, transfer it into the appropriate tube or draw the sample directly into the appropriate tube.

  • Make sure you remove the stopper from the tube and the needle from the syringe before dispensing the sample into the blood collection tube to avoid haemolysis.
  • The ratio of blood to anticoagulant is very important: Fill sodium-citrate tube always to the line. EDTA and Lithium Heparin tubes should be at least half-full.

If not enough blood is added into the collection tube you may see:

  • A false decrease in hematocrit value due to dilation of the blood
  • A false decrease of analyte values due to dilation of the blood
  • Inaccurate MCV, MCH, MCHC and HGB
  • Altered red cell shape: erythrocytes will shrink due to high osmolality of the anticoagulant fluid
  • Artifactually prolonged clotting time.


Order of Filling

It is recommended to follow the correct order of filling tubes to avoid cross-contamination of additives. The sodium citrate tube is to be filled first, followed by the serum tube, the lithium heparin tube and any EDTA tubes last of all. Filling out of order may lead to contaminating the blood samples with additives and lead to invalid results in major biochemical parameters.


Sample Mixing

When: Immediately following collection.

Why: To properly mix the blood and anticoagulant. To prevent formation of clots that will interfere with cell counting.

How: Holding tube upright, gently invert 180 degrees and back. Ensure that it is thoroughly mixed by inverting the tube 8-10 times.

Be Careful: Avoid shaking samples. This can lead to haemolysis. Do not transfer blood from one tube to another e.g., EDTA to Lithium Heparin.

If Not Mixed: The specimen may need to be re-drawn if blood clots form or, if mixed too vigorously, haemolysis occurs.


Storage After Collection

Storage At Room Temperature

Analyse Lithium Heparin whole blood within 60 minutes, EDTA whole blood within 3 – 4 hours, Plasma/Serum within 5 hours.

Please note that storing whole blood or centrifuged but unseparated serum or plasma (allowing prolonged contact with cells) can result in hypoglycaemia , hyperkalaemia and haemolysis.

EDTA whole blood: 8 hours, plasma or serum: 24-48 hours if stored at 2-8 degrees.

Storage at -10 degrees is not appropriate for whole blood, serum or plasma up to 5 weeks.

Bioscint Engineering supplies a wide range of tubes and consumables for blood collection including centrifuges. Kindly visit our online shop or contact us directly for more information.

Source: Zoetis

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