Item Brochure

Preanalytical Variables
46-68% of all laboratory errors occur in the preanalytical phase
1
, and 12.5%
of preanalytical laboratory errors may cause an erroneous medical decision
2
.
In order for results to be as accurate as possible and to reduce the number
of samples that need to be re-drawn, it is important to be aware of
preanalytical variables in the laboratory.
7
Order of draw – for multiple samples.
1. Blood Culture Bottles
2. Coagulation Tubes
3. Non-Additive Tubes
4. Additive Tubes.
Coagulation tubes should be taken before plastic serum tubes as the clot
activator in plastic serum tubes may affect coagulation test results.
Tourniquet time
The tourniquet must be loosened after no more than one minute. If applied for
longer the pressure from the tourniquet may cause elevated potassium levels.
The tourniquet should be positioned 7.5cm to 10cm above the puncture site.
Mixing
Most tubes contain an additive. Regardless of the additive type, all tubes should
be gently inverted to ensure thorough mixing of the blood with the additive.
Tubes with anticoagulants such as EDTA, heparin etc., must be mixed to ensure
that the specimen does not clot. For example insufficient mixing could lead to
platelet clumping in EDTA tubes. Tubes with a clot activator such as BD Plus
Serum Tubes must also be mixed or the specimen may not clot completely in
the recommended time.
Light sensitive analytes
These include Bilirubin, Erthrocyte Protoporphyrin and Carotene. They must be
transported in appropriate materials, such as foil, or should be collected in a
light sensitive tube otherwise results may be affected.
Storage of tubes
Store all tubes at 4-25ºC (39-77ºF), unless otherwise noted on the package
label. Extreme temperatures can reduce the effectiveness of the tubes and
cause abstract results. Always remember to rotate your stock.
Venepuncture site
Veins that have thickened walls are harder to puncture than normal. In such
circumstances, or if the chosen vein has been damaged by frequent venepunc-
tures, it is best to look for another vein at a different site.
Centrifugation speed
Never centrifuge glass tubes above 2200g in a horizontal head (swinging bucket)
centrifuge or above 1300g in fixed angle centrifuge heads, as breakage may
occur. The clotting of a sample must be fully completed before centrifugation of
serum tubes. Specific centrifugation instructions are described in the instructions
for use provided with each product package.
1. Source Becan-Mcbride K. Laboratory Sampling: Does the Process Affect the Outcome? Journal of Intravenous Nursing May – June
1999; Vol. 22, No. 3
2. Source: M. Plebani Carraro P. Mistakes in a stat Laboratory: types and frequency. Clinical Chemistry. 1997; 43:8 1348-1351
BD Vacutainer
®
systems follow the Clinical and Laboratory Standards Institute (formerly NCCLS) Guidelines.