Blood collection tubes

A blood collection tube is used in medicine as a sample container for taking and processing blood samples . Systems for urine samples have a similar structure . It also enables uncomplicated transport and short-term storage of the samples taken.

Blood collection tubes are made of transparent plastic and have a special connector at the tip. Among other things, there are adapters for the Luer lock system .

Structure and functionality

Blood collection tubes of the aspiration principle. The different color coding according to EN 14820 correspond to the different functions:
(1) Serum gel tubes (brown)
(2) Heparin tubes (orange)
(3) EDTA tubes (red, large)
(4) Citrate coagulation tubes (green )
(5) EDTA tubes (red, small)
(6) ESR (citrate) tubes (purple)

Blood sampling according to the negative pressure principle

There are two fundamentally different systems that take up the samples through aspiration or negative pressure. For both systems there are tubes with different accessories that are standardized and color-coded.

Aspiration system

A blood collection tube using this system (e.g. Kabevette® , Monovette® ) corresponds to the structure of a syringe . By pulling out the stamp, a negative pressure is created, which accelerates the blood withdrawal . The stamp can be snapped off after it has been completely pulled out, which simplifies the shipping and storage of the Monovette by shortening its length. Since the plunger engages when fully withdrawn, a negative pressure can be generated with a Monovette even before the puncture so that blood can also be drawn with a Monovette according to the negative pressure principle Monovette may be connected, otherwise there will be no negative pressure in the Monovette due to pressure equalization via the cannula.

A monovette can therefore be used both according to the aspiration principle and the vacuum principle.

Vacuum system

Within the sample container of this type (eg. B. Vacuette® , Vacutainer® ) there is a priori a negative pressure. If it is placed on the adapter connected to the puncture cannula, the blood is sucked in by this negative pressure. One advantage of this system is that the amount of blood drawn in is more constant than with the Monovette. The disadvantage compared to the aspiration system is that the negative pressure built up for taking blood cannot be varied and can be adapted to the vein conditions.

Color coding

Depending on the additive used to inhibit blood coagulation (depending on the type of analysis required), a distinction is made between different types of collection tubes:

Citrate (green (Monovette) or light blue (negative pressure), e.g. for INR / Quick , PTT , D-Dimer determination)
EDTA (red (Monovette) or purple (vacuum), for. Example, for the blood , HbA ₁ c or blood typing )
Lithium - heparin (yellow-orange (Monovette) or green (negative pressure), for clinical chemistry )
Serum gel (white or beige (Monovette) or red (negative pressure), for clinical chemistry , serology )
Sodium citrate (purple (Monovette, also called Sedivette) or black (negative pressure), specially shaped tube to determine the blood sedimentation reaction )
Sodium fluoride (light yellow (Monovette) or gray (negative pressure), e.g. for lactate or glucose )