. The counting of the cellular elements of the blood (erythrocytes, leukocytes, and platelets) is based on the classic method of electrical impedance.
Electrical resistant principle, which depend on the fact that blood cells are non conductive to electricity, so when they pass through electrical field they will increase the electrical resistance. The counting chamber consists of a beaker, two electrodes with a direct current, an orifice with specified dimension; when suspended cells passes through the aperture it will increase the electrical impedance between the two electrodes, manifested as a pulse (sum of pulse= count).
The pulse height indicate cell volume. The aspirated whole blood specimen is divided into two aliquots and mixed with an isotonic diluent. The first dilution is delivered to the RBC aperture bath, and the second is delivered to the WBC aperture bath. In the RBC chamber, both the RBCs and the platelets are counted and discriminated by electrical impedance. Particles between 2 and 20 fL are counted as platelets, and those greater than 36 fL are counted as RBCs. Red cell histograms: histograms are derived by plotting the size of each red cell on x axis and the relative number on the y axis.
They are used to determine the average size, distribution of size, and to detect sub populations. A reagent to lyse RBCs and release hemoglobin is added to the WBC dilution before the WBCs are counted by impedance After the counting cycles are complete, the WBC dilution is passed to the hemoglobinometer for hemoglobin determination (light transmittance read at a wavelength of 535 nm). Hemoglobin, on most automated systems, is measured as cyanmethemoglobin.
Automated CBC Parameters. Quality Control. Joanna Ellis, MLS(ASCP). Revised Keri Brophy-Martinez. The Automated Complete Blood Count.
Red cells are lysed and potassium ferricyanide oxidizes hemoglobin to methemoglobin, which combines with potassium cyanide forming cyanmethemoglobin. The brown color is measured spectrophotometrically and the corresponding hemoglobin reported. Normal rang. Males 14-18 g/dl.
Females 12-16 g/dl. The white blood cell differential count determines the number of each type of white blood cell, present in the blood. It can be expressed as a percentage (relative numbers of each type of WBC in relationship to the total WBC) or as an absolute value (percentage x total WBC). Of these, the absolute value is much more important than the relative value. There are five basic white blood cell types:.
Neutrophils. Eosinophils. Basophils.
Lymphocytes. Monocytes Each WBC cell type has its' own unique features. Inability of blood to supply tissues with adequate oxygen for proper metabolic function. Usually associated with decreased levels of hemoglobin or hematocrit (packed red cell volume) Usually associated with decreased RBCs. Diagnosis made by patient history, physical examination, signs and symptoms, and hematological laboratory findings. Classified as moderate (Hb 7-10 g/dl) or severe (Hb.
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