3. Blood Cell Histograms:

Transcription

1 LECTURE MODULE 6c: ELECTRONIC CELL COUNTING PART III 3. Blood Cell Histograms: a. The Coulter cell counters today provides size distributions of the cellular content: 1) volume given in µm 3 or fl vs relative number or frequency 2) distributions given for Plts., WBCs, and RBCs b. Distributions are plotted as histograms on a x- y plotter or matrix printer c. Cells in the WBC counting baths larger than 45 fl are counted and plotted as WBCs 1) The WBC histogram results in 3 distribution peaks - a) The 1st peak (45 to 90 fl) represents the lymphocytes b) The 2nd peak from 90 to 160 fl represents the mononuclear cell population i. this a minor population and normally represents the monocytes, but can also represent abnormal cell types such as the immature precursor cell types found in leukemia c) The major population and peak begins at 160 and ends about 450 fl. This population is more spread out an represents normal mature types of granulocytes 1

2 2) The percent of each cell type is calculated combining the distribution values and the total WBC distribution spread 3) The latest models can give a five part differential; %Lymphs, %Monos, %Gran %Eos %Baso 4) An absolute count of each cell fraction is also given: % cells X total WBC count 5) These estimations are often useful as a screening test or as a check on WBC differentials - instruments are surprisingly accurate when compared with the slide diff d. Cells in the RBC counting baths in the size range of 36 to 360 fl are counted and frequency is plotted on the histogram RBC scale 1) normal single peak between fl 2) peak should coincide with the MCV e. Cells in the RBC counting baths in the size range between 2 to 20 fl are counted and frequency is plotted on the histogram platelet scale 9. Explain the principle of blood cell histograms and the individual populations of blood cells reported. 2

3 Normal Blood cell Histogram 10. Diagram a normal blood cell histogram. f. Abnormal WBC Histogram patterns: 1) The lower threshold is 45 fl, but the histogram will extend lower to pick up abnormalities 2) Error Flags: a) "R" ags signal irregularities in the WBC distribution, and will next to the differential parameters. The "R" stands for the region, and the following numeral indicates the location in which the interference was detected i. R1: interference in the valley to the left of the lymphocyte peak ( 35 fl) - CAUSES - Sickled RBCs, nucleated RBCs, or clumped or giant platelets will appear in this area and artificially raise the WBC ct. 3

4 R1 WBC 75.2 LY% 75.2 MO% 9.6 GR% 15.2 LY# 2.9 MO# 0.4 GR# 0.6 * Normal Abnormal ii. R2: excessive overlap of cell populations at the lymphocyte/mononuclear cell boundary ( 90fL) CAUSES- presence of abnormal cell types such as atypical lymphs, blasts, or plasma cells R2 * Normal Abnormal iii. R3: excessive overlap of cell populations at the mononuclear/ granulocyte boundary ( 160 fl) CAUSES; increased presence of more immature granulocytes (bands), referred to as a maturation SHIFT TO THE LEFT R3 * Normal Abnormal 4

5 iv. R4: extension of the cell distribution at the upper end of the WBC threshold ( 450 fl) CAUSE; most commonly when the granulocyte population is very high R4 * Normal Abnormal b) Other signal ags: i. H: value is greater than the present high normal limit ii. L: value is lower than the present low normal limit 11. Compare and contrast the different WBC channel R" signal ags and the meaning of each. g. Abnormal RBC Histograms: 1) The normal RBC histogram reects normal MCV as-well-as normal RDW a) A normal distribution begins above 50 fl and will peak between fl 5

6 NORMAL RBC HISTOGRAM Toe b) The extended distribution called the toe is normal, and represents duplicates, triplicates, agglutinated RBCs, aperture artifacts, and a occasional WBC 2) An increased MCV will shift the curve to the right, and a decreased MCV will shift the curve to the left. An increase in RDW will be reected by an increase in the "width" of the area beneath the curve. NORMAL ABNORMAL MCV: 105 RDW: ) In some disorders there may be two size populations of RBCs, i.e.. a microcytic population and a macrocytic population of cells. The RBC histogram will reect this abnormality. NORMAL ABNORMAL

7 h. Atypical Platelet Histograms: 1) Can result in some disorders due to the presence of large platelets Examine a RBC channel histogram and a platelet histogram and judge weather the histogram pattern is normal or abnormal. 4. X-BAR B (X B ) STATISTICAL ANALYSIS: a. BACKGROUND: Research has shown that RBC indices (MCV, MCH, and MCHC) of patient populations are stable over time. - This stability is the basis of a hematology Q.C. technique known as X B analysis. b. FUNCTION: To quickly determine the direction and amount of change, daily, due to the instrument, the reagents, or sample handling. c. HOW IT WORKS: 1) "Target" values of MCV, MCH, and MCHC are determined by calculating the mean of 250 to 1000 samples for each parameter. 2) Once target values are determined, the analysis can be applied using small sample "batches" of 20 samples. 3) The mean and standard deviation of each batch is compared to the target value of each parameter, and averaged in with the mean and standard deviation of the previous batches. 7

8 d. The hematology system is considered "in control" when the batch means are within established standard deviation limits of the target values. e. The %-difference between each batch mean and its corresponding preset target value can be calculated and displayed on a Levy-Jennings graph. Formula for X-Bar-B THE END 8