Types of Blood Samples, Criteria for rejection of the blood sample, Color coding of the blood sample tubes
Blood samples types:
- The blood sample from the patients is of various types according to the type of blood tests.
- These blood sample timings are also critical, and some of the tests may need a fasting sample, while some tests may be done on random samples.
- Venous blood:
- This is the easiest way to collect the blood sample.
- It is free of complications.
- Blood is taken from the superficial veins.
- The commonest site is the antecubital fossa because of the presence of basilic vein, cephalic vein, median cubital veins are the commonest veins.
- Veins of the wrist or hand may be used.
- Another site is the femoral vein.
- Arterial blood:
- Arterial blood is used to measure arterial blood gases, like oxygen, CO2, and pH.
- Arterial puncture is more difficult than the venous sample.
- The Brachial and radial arteries are often used; the femoral artery is usually avoided because of bleeding.
- Capillary blood:
- It is mostly used in the pediatric patient’s group where there is no need for a large amount of blood.
- The common sites are the fingertips, heel, and ear lobe. The heel is most commonly used in infants.
Criteria for the rejection of the blood sample:
- Blood samples are not labeled or not properly labeled.
- Insufficient blood quantity.
- Blood sample showing hemolysis.
- A wrong collection tube is used.
- Insufficient quantity of the anticoagulants.
- Improper transport of the sample.
Nowadays, there are commercially color-coded tubes available:
- The following table shows their color and the purpose of the use:
Stopper tube Additives Outcome of additive Purpose of use Test tubes Red
- N0 anticoagulant
- No additives
- Blood banking
- Anticoagulant, for plasma
- Remove calcium and prevent clotting.
- Invert tube 6 to 8 times
- Best for hematology
- Accelerate clot usually in 5 minutes, for serum formation
- It should be inverted 8 times.
- All serum test
Light Blue Sod. Citrate
- anticoagulant binds calcium.
- Get blood or plasma
- Coagulation studies
- PT, APTT, factor assay
Gray Na fluoride/K oxalate
- Inhibit glycolysis
- Anticoagulant, remove Ca++ to prevent clotting.
- Get whole blood or plasma.
- Alcohol level
- Na+ Heparin
- Lithium Heparin
- Ammonium Heparin
- Inhibit thrombin activation to prevent clotting.
- Get whole blood or plasma.
- Invert the tube 7 to 10 times to prevent clotting
- Ammonia level
- Arteria blood gases
- Carboxy Hb
- Plasma chemistry
- Prevent blood from clotting
- Stabilize bacterial growth
- Invert the tube 8 times to prevent clotting
Blood culture Glod
- Clot activator
- Clot activator shortens the time for clot formation.
- The gel forms a separator between cells and serum.
- Invert tube 5 times and centrifuge after the clot formation
- Most chemistry tests
- Not good for blood banking
- Gel separator
- Lithium heparin
- Heparin prevents clotting
- The gel prevents cell contamination.
Potassium determination Black
- Na + citrate
- Binds Ca++
- 4:1 ratio of blood to anticoagulant
Westgreen ESR determination
Summary of the color-coded blood collection tubes:
- Red top tube = No additives for chemistry tests.
- Blue top = Coagulation studies.
- Green top = For general purpose, blood gases, chemistry.
- Lavender top = For CBC and hematology.
- Gray top = For chemistry and glucose.
- Yellow top = For blood culture.
Contents difference between plasma and Red blood cells:
|Contents||Plasma||Red Blood Cells|
|Nonprotein nitrogen mg/dL||8.0||40|
- Above is a picture presentation of test tubes.