Ficoll separation of whole blood clotting

Blood draw - test material whole blood, EDTA, plasma and serum

Most laboratory tests are performed on blood.

One differentiates:

  • Whole blood, with / without additives: contains all cellular components, coagulation factors and serum
  • Serum: consists of the supernatant after coagulation (in tubes with coagulation activators) and subsequent centrifugation of whole blood
  • Plasma: consists of the supernatant after centrifugation of whole blood with the addition of anticoagulants (EDTA blood, citrate blood, heparin blood)
  • CF blood: Inhibition of the breakdown of glucose and thus also the synthesis of lactate, e.g. for the determination of glucose, especially in OGTT

Order these blood collection systems from our partner Intermed:
Freecall: 0800 0850-113 Freefax: 0800 0850-114

Please click here to go directly to Intermed.

Whole blood without additives

Whole blood should be centrifuged after coagulation, i.e. after 20-30 minutes of standing rest, otherwise in vitro metabolic processes such as glycolysis take place. Storage of a whole blood sample for 48 hours at room temperature leads to a decrease in the glucose concentration of 54% and an increase in the phosphate by 90%. Potassium can also accumulate considerably in the serum.

Danger: Do not store non-centrifuged blood in the serum collection tube in the refrigerator. Due to the temperature dependence of the Na + - / K + -ATPase, potassium is released from the cells at temperatures <4 ° C and> 30 ° C.

EDTA blood

Special features for blood counts

  • EDTA blood for the small blood count is stable for 24 hours at room temperature.
  • EDTA blood for the complete blood count (cell differentiation) requires samples that are, if possible, not older than 8 hours and that have been stored at room temperature. With progressive degeneration of the leukocytes, their ability to be assessed decreases sharply with increasing time.

Special features for blood group serology

  • The EDTA blood for blood group and antibody determination is stable for a maximum of 5 days.
  • In addition to the barcode, the tubes must be labeled with the patient's surname, first name and date of birth.

LADR informs No. 258: Targeted rhesus prophylaxis - injections only when necessary

Citrate blood

Special features for coagulation studies

  • The citrate tube must must be filled up to the mark, otherwise the blood will be diluted with the liquid contained. In concrete terms, the correct ratio of citrate to blood is then not given. For the subsequent coagulation diagnosis, a defined amount of calcium is added to the sample in order to start the coagulation in a controlled manner. If the citrate / blood ratio were shifted, the results obtained would be falsified.
  • If only a citrate tube is withdrawn when taking blood, a small amount of blood should first be withdrawn into a tube that is to be discarded, because the dead volume of the withdrawal system (cannula, tube) can lead to an error in the citrate-blood ratio .
  • Hemostasis samples have to get to the laboratory quickly. Information on correct preanalytics can be found under the respective parameters in the A-Z laboratory medicine list of services.
  • Citrate platelet poor plasma should be frozen immediately after collection (-20 ° C to -70 ° C). To do this, the citrate blood is centrifuged, the supernatant is pipetted into a new sample tube (do not pour it off!) And centrifuged again while protecting the leukocyte separating layer. The supernatant (low-platelet citrate plasma) that has been pipetted off again is placed in a new sample tube and frozen immediately. Insufficiently centrifuged samples contain residual platelets that break down at low temperatures. The components released in the process lead to incorrect measurements.

Learn more about Potential Blood Collection Errors for Coagulation Analysis

Whole blood serum and plasma

Separation gels form a stable separating layer between the serum or plasma and the blood cells after centrifugation, so that even after days no cell constituents enter the serum.

Advantages of separation gels:

  • longer shelf life at 4-8 ° C without disturbing influence by the cells (e.g. glucose breakdown or potassium release)
  • higher material yield in improved quality
  • reduced risk of confusion and infection
  • no coagulation if carried out correctly

serum

  • Blood collection: tubes without additives, tubes with coagulant additives (beads, ...), tubes with coagulation activators and separating gel
  • Mix the sample well: tilt it 180 ° five times, don't shake!
  • Allow the sample to drain out for 20-30 min
  • Centrifugation: after clotting is complete, 10 min at 2000 × g
  • then separation of cellular components, unless a tube with separation gel was used
  • Supernatant: without coagulation factors (except calcium)

Danger:Do not freeze the serum until it has been drained!

plasma

  • Blood collection: tubes with anticoagulant additives (EDTA, citrate, Na-, NH4-, Li-heparin, hirudin ...)
  • EDTA, citrate: bind calcium ions
  • Heparin: activates antithrombin III by binding
  • Hirudin: blocks thrombin by binding
  • It is essential to pay attention to the correct filling level in order to achieve correct mixing ratios!
  • Mix the sample well: tilt it 180 ° five times, don't shake!
  • Centrifugation possible immediately; 15 min at 2000 x g
  • then separation of cellular components
  • Supernatant: contains fibrinogen and other coagulation factors

Danger:If possible, a separate tube should be removed for plasma collection. Simply pipetting off the plasma from the centrifuged whole blood tube leads to massive changes in concentration in the remaining whole blood tube! To obtain plasma from an original tube, double the amount of whole blood (serum + hematocrit) of the required plasma volume should be transferred from the original tube into a separate vessel and only then centrifuged.

General storage and shipping conditions for blood samples

  • Cooling: Serum / plasma must be cooled immediately after centrifugation (4–8 ° C) Exception: cryoglobulins, cold agglutinins and cryofibrinogens (allow to clot at 37 ° C and centrifuge warm, see A – Z section)
  • Freeze: Material may only be frozen once, the cold chain may not be interrupted, transport in special ice packs
  • Light protection: Exposure to light can lead to a decrease in e.g. bilirubin, porphyrins, folic acid, β-carotene, vitamins A, C, K, B1, B2 and B6, protect samples from exposure to light (e.g. wrapping with aluminum foil).

Guidelines for the stability of blood samples

Substance groupBlood sample stability

Enzymes

chilled for up to 5 days without a deviation of more than 10%

Exceptions:

  • LDH (activity decreases due to the cold instability of LDH4 and LDH5)
  • acid phosphatase (is only stable when acidified)

Substrates

refrigerated for up to 6 days without significant changes

Exceptions:

  • Triglycerides, endogenous lipases, split off fatty acids
  • Electrolytes, LDH, bilirubin: stability up to 24 hours
  • Blood lipids, folic acid, vitamin B12: stability up to 48 hours

Plasma proteins

refrigerated for up to a week

Exceptions:

  • Coagulation tests (citrate plasma, shelf life approx. 4 hours)

Hormones,
Tumor markers

at room temperature for 3 days

Exceptions:

  • NSE must be sent in chilled
  • if the analysis for the determination of peptide hormones (in particular: ACTH, renin,
    Vasoactive intestinal peptide, proinsulin and calcitonin) cannot take place on the same day,
    the material must be sent in frozen
  • First trimester Screenig: Whole blood is stable for 6 hours when refrigerated, centrifuged
    Serum is stable for 24 hours if refrigerated, should be sent frozen
Order these blood collection systems from our partner Intermed:
Freecall: 0800 0850-113 Freefax: 0800 0850-114

Please click here to go directly to Intermed.

Status: 02/26/2021