Platelet Counts
Platelets: Platelets are the smallest formed elements in the blood, normally ranging in size from 2-4 microns. Platelets function in the coagulation of blood. A normal platelet count is 150,000-400,000/c.mm.Platelets formation (thrombopoiesis) occurs in bone marrow, by budding off from megakaryocytes. Around 1011 platelets are produced each day by an average healthy adult. The lifespan of circulating platelets is 5 to 9 days. Each megakaryocyte produces between 5,000 and 10,000 platelets.
Objectives : To determined the platelate count of the provided sample.
Procedure \ Materials needed: Whole fresh blood. RBC Pipette. Ammonium oxalate 1%, in a distalled water. Hemacytometer chamber. Microscope. Petridish. Pipette rotator. Filter paper. Alcohol.Procedure: Using RBC Pipette with drawn blood to exactly 0.5 mark; then dilute to 101 mark with ammonium oxalate(dilution 1:200). Place the pipette on a pipette rotator for 10-15 minute to ensure complete haemolysis of RBC'S. Discard the first five drops from the RBC pipette and fill besides of the haemocytometer.
Placed the haemocytometer in a moist petridish; and leave it for 20-30 min.(this allow the platelate to settle and prevents evaporation of fluid). Put the haemocytometer on microscope and exam. Under power 10x. Then change the exam. to power 40x; the plat. appears round or oval bodies with alight purplish sheen( fine process may be seen). The platelate are counted in the central big square (which contain 25 small squars). Counting the no. of plat. in both sides of chamber; add two count to other and determined the average number of platelets counted.
Interpretation of Results: Thrombocytopenia:Platelet counts below normal: A plastic anemia. Pernicious anemia. Acute leukemia's. Idiopathic thrombocytopenic purpura.
Thrombocytosis: Platelet counts above normal: Polycythemia vera. Hemolytic anemia. Chronic myeloproliferative disorders. After splenectomy.
Sources of Error: A. Light adjustment is critical. If the condenser is not lowered it will fade out the platelets. B. Bacteria and debris can be misinterpreted as platelets. This type of artifact is generally much more refractile than platelets. C. Clumping of platelets sometimes occurs, and if so the specimen must be recollected. EDTA is the anticoagulant of choice for preventing platelet clumping. D. General hemacytometer errors, i.e. overloading chamber, counting wrong borders.