Practical Hematology - Blood Tubes & Anticoagulants

03/11/1444 By Abdulfatah albakkosh Type of blood tubes • The anticoagulant type is shown by the colour of the evacuated sample tubes, which are sterile and colour coded. • For a complete blood picture, a sample of whole blood must be taken in an EDTA tube. For other tests, like biochemistry or ser...

03/11/1444 By Abdulfatah albakkosh Type of blood tubes • The anticoagulant type is shown by the colour of the evacuated sample tubes, which are sterile and colour coded. • For a complete blood picture, a sample of whole blood must be taken in an EDTA tube. For other tests, like biochemistry or serology, serum must be taken from blood collected in a plain tube. 03/11/1444 Anticoagulants • Whole blood or plasma is required for the majority of haematology and coagulation procedures. • To avoid coagulation, the blood is mixed with an anticoagulant as soon as it is collected from the patient. • Haematology laboratories often use three anticoagulants: 03/11/1444 1 – EDTA ( Ethylenediaminetetra-acetic acid) • EDTA salts are powerful anticoagulants and may be used in all haematological procedures. • As a dipotassium or tripotassium salt (EDTA-K3), it's often available in liquid or spraycoated form, and the dosage is usually 1.50 - 2.50 mg/ml of blood. • Therefore, care must be taken to ensure that the right quantity of blood is used. • In order to keep the blood from coagulating, EDTA binds to calcium molecules in the blood. • Both RBCs and leukocytes are affected by an excess of EDTA, resulting in a reduction in PCV, an increase in MCHC, and shrinkage. Another effect is the swelling of the platelets. 1 – EDTA ( Ethylenediaminetetra-acetic acid) • In fact, most tests require that the sample be used within a few hours after being collected. • For several tests, such as the complete blood count (CBC) and platelet count, the sample stability may be maintained for up to 24 hours at 4 C. Blood should be processed within three hours of collection if peripheral blood smears are to be performed. 03/11/1444 2 – Sodium citrate • In coagulation tests, the anticoagulant of choice is trisodium citrate (32 g/l). • A one-volume solution of sodium citrate is mixed with nine volumes of blood. This is done right away, and the mixture is well mixed. • It prevents blood clotting by binding to the calcium in the blood. • It is also the most common anticoagulant used to measure ESR (4 volumes of blood mixed with 1 volume of sodium citrate). 3 – Heparin • may be used at a concentration of 15–30 iu/ml of blood. • Coagulation is prevented by its interaction with antithrombin–III and subsequent inhibition of thrombin. • The use of heparin does not alter the size of the RBC but may cause clumping of the WBC and platelets. It is, therefore, of limited use in haematology routine work. • is the anticoagulant of choice for only a special test (osmotic fragility test) in a ratio of 9 volumes of blood to 1 volume of heparin. • In addition, heparin causes morphologic distortion of platelets and WBC and tends to cause bluish discolouration of the background of a blood smear stained with a Romanowsky stain. 03/11/1444 Heamoglobin • Red blood cells include the protein molecule haemoglobin (Hb), which transports oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues to the lungs. Normal range for Hb : males 13.5 – 17.5 g/dl( gram per deciliter), female 12.0 - 15.5 g / dl . Anemia is characterised by a reduction in the concentration of haemoglobin in the blood, whereas polycythemia is characterised by an increase in the concentration of haemoglobin. The concentration of haemoglobin must be accurately measured in order to provide an accurate diagnosis.