Page 19 - pathology_services_handbook_5th_edition_2018

Order of draw

Order of draw can be defined as sequence of blood inoculation into specimen container
HTAA, KUANTAN Optimum Volume for Tube’s Collection
to prevent cross contamination whenever multiple tubes are used.

All collection tubes need to be filled to the correct volume to ensure the proper
•
amount of blood for the amount of additives in the tube.
Blood has to be transfer immediately from the syringe into tubes to prevent
•
clotting.
UNDERFILLED : Insufficient for running the test.
: Higher concentration of additives blood ratio.
OVERFILLED : Potential for clotting.
: Lower concentration of additives to blood ratio.

Blood collection from IVs and catheters

• Blood should not be collected proximal to an IV site but preferably from the other
arm.
• If samples must be obtained from a catheter, heparin contamination and dilution
must be avoided. The line should be flushed with 5.0 ml of saline and the first 5.0
ml of blood or six dead space volume of the catheter discarded.
• If a syringe is used, a small volume (< 10.0 ml) syringe is recommended so that
clotting in the syringe during phlebotomy can be avoided.

AVOIDING HAEMOLYSIS

Haemolysis should be avoided because it invalidates certain laboratory determinations.
The presence of haemolysis of moderate or greater degree adversely affects the blood
specimen in several ways.

It releases erythrocytes contents such as Potassium, Lactate dehydrogenase and Acid
phosphatase into the serum. Thereby, elavating their levels.

It colours the blood plasma and serum which will interfere with colorimetric assays
especially photometric measurements using shorter wavelengths of the visible
spectrum.

As some red blood cells have been damaged, the packed cell volume (PCV) and red
blood cell (RBC) count will be falsely depressed. Although the haemoglobin value will
be accurate, the calculated red blood cell indices will be affected by the depressed PCV
and RBC.
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