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International Society of Blood Transfusion (ISBT) Working Party has organized red cell antigens into 25 blood group systems. Red cell antigens that are produced by alleles (alternative forms of a specified gene) at a single gene locus or very closely linked loci constitute a blood group system.
Blood transfusion is a life-saving procedure in an appropriate setting and there are no side-effects in the majority of cases. However, it is a potentially harmful procedure and every recipient of transfusion is at risk of an adverse reaction. It should be prescribed only if there is a definite clinical…
Porphyrias (from Greek porphura meaning purple pigment; the name is probably derived from purple discoloration of some body fluids during the attack) are a heterogeneous group of rare disorders resulting from disturbance in the heme biosynthetic pathway leading to the abnormal accumulations of red and purple pigments called as porphyrins…
This is done by flow cytometric analysis for detection of lack of GpIb/IX in Bernanrd Soulier syndrome (deficiency of CD42), and lack of GpIIb/IIIa in Glanzmann’s thrombasthenia (deficiency of CD41, CD61). What is the best protocol for platelet glycoprotein (GPIIb/IIIa) analysis using flow cytometry? Fresh platelets should always…
D-dimer is derived from the breakdown of fibrin by plasmin and D-dimer test is used to evaluate fibrin degradation. Blood sample can be either serum or plasma. Latex or polystyrene microparticles coated with monoclonal antibody to D-dimer are mixed with patient’s sample and observed for microparticle agglutination. As the particle…
FDPs are fragments produced by proteolytic digestion of fibrinogen or fibrin by plasmin. For determination of FDPs, blood is collected in a tube containing thrombin (to remove all fibrinogen by converting it into a clot) and soybean trypsin inhibitor (to inhibit plasmin and thus prevent in vitro breakdown of fibrin).…
Automated hematology analyzers work on different principles: Electrical impedance Light scatter Fluorescence Light absorption Electrical conductivity. Most analyzers are based on a combination of different principles. (1) Electrical impedance: This is the classic and timetested technology for counting cellular elements of blood. As this method of cell…
AUTOMATED HEMOTOLOGY ANALYZER Automation is a process of replacement of tasks hitherto performed by humans by computerized methods. Until recently, hematological tests were performed only by manual methods. These methods, though still performed in many peripheral laboratories, are laborintensive, and involve use of hemocytometers (counting chambers), centrifuges, Wintrobe tubes, photometers,…
CAUSES OF ERRONEOUS RESULTS (INTERFERENCES CAUSING ABNORMAL RESULT) These are listed in Table 809.1 Table 809.1 Causes of erroneous results with hematology analyzer Parameter Interfering factors Erroneous increase Erroneous decrease 0. All parameters — Clotted sample 1. WBC count Nucleated red cells Large platelet clumps Unlysed red cells…
Parameters measured by hematology analyzers and their derivation are shown in Tables 808.1 and 808.2. Most automated hematology analyzers measure red cell count, red cell indices (mean cell volume, mean cell hemoglobin, mean cell hemoglobin concentration), hemoglobin, hematocrit, total leukocyte count, differential leukocyte count (three-part or five-part), and platelet count.
FLOW CYTOMETRY Flow cytometry is a procedure used for measuring multiple cellular and fluorescent properties of cells when they flow as a single cell suspension through a laser beam by a specialized instrument called as a flow cytometer. Flow cytometry can analyze numerous cells in a short time and…
Fluorescence A fluorochrome absorbs light energy and emits excess energy in the form of photon light (fluorescence). Fluorescence is the property of molecules to absorb light at one wavelength and emit light at a longer wavelength. The fluorescent dyes commonly used in flow cytometry are fluorescein isothiocyanate (FITC) and…
Leukemias and lympomas: Immunophenotyping (evaluation of cell surface markers), diagnosis, detection of minimal residual disease, and to identify prognostically important subgroups. Paroxysmal nocturnal hemoglobinuria: Deficiency of CD 55 and CD 59. Hematopoietic stem cell transplantation: Enumeration of CD34+ stem cells. Feto-maternal hemorrhage: Detection and quantitation of foetal hemoglobin in maternal…
Platelet aggregation tests are carried out in specialized hematology laboratories if platelet dysfunction is suspected. These tests are usually indicated in patients presenting with mucocutaneous type of bleeding and in whom screening tests reveal normal platelet count, prolonged bleeding time, normal prothrombin time, and normal activated partial thromboplastin time.
A blood smear is examined for: Red cells: Morphology, immature forms, inclusion bodies, arrangement of cells. White cells: Differential count, abnormal or immature forms. Platelets: Adequacy, abnormal forms. Parasites: Malaria, filaria. A peripheral blood smear has three parts: Head, body, and tail. Also read: PREPARATION OF BLOOD SMEAR…
