Title 11. HAEMATOLOGICAL TESTS.pdf ✅

PHARMD GURU Page 1 HAEMATOLOGICAL TESTS Blood contains three types of formed elements: 1) Red blood cells (RBCs), 2) White blood cells (WBCs), and 3) Platelets. A CBC (Complete blood count) typically includes RBC count, total WBC count, hemoglobin (Hb), haematocrit (Hct), RBC indices (mean cell volume [MCV], mean cell Hb [MCH], mean cell Hb concentration [MCHC]), reticulocyte count, and platelet count. A. RBCs (erythrocytes) 1. The RBC count, which reports the number of RBCs found in a given volume of blood, provides an indirect estimate of the blood’s Hb content. Values are often reported in cells/microliter or cells/litre and less commonly as cells/cubic millimetre (mm3). Normal values are: a. 4.3 to 5.9 X 1012 cells/L of blood for men b. 3.5 to 5.0 X 1012 cells/L of blood for women CLINICAL LABORATORY TESTS USED IN THE EVALUATION OF DISEASE STATES, AND INTERPRETATION OF TEST RESULTS
PHARMD GURU Page 2 2. The Hct or packed cell volume (PCV) measures the percentage by volume of packed RBCs in a whole blood sample after centrifugation. The Hct value is usually three times the Hb value and is given as a percentage or fraction of 1 (42% to 52% or 0.42 to 0.52 for men; 37% to 47% or 0.37 to 0.47 for women). a. Low Hct values indicate such conditions as anaemia, over hydration, or blood loss. b. High Hct values indicate such conditions as polycythemia Vera or dehydration. 3. The Hb test measures the grams of Hb contained in 100 mL (1 dL) or 1 L of whole blood and provides an estimate of the oxygen-carrying capacity of the RBCs. The Hb value depends on the Number of RBCs and the amount of Hb in each RBC. 4. RBC indices provide important information regarding RBC size, Hb concentration, and Hb weight. They are used primarily to categorize anemias, although they may be affected by average cell measurements. A peripheral blood smear can provide most of the information obtained through RBC indices. Observations of a smear may show variation in RBC shape (poikilo cytosis), as might occur in sickle-cell anemia, or it may show a variation in RBC size (anisocytosis), as might occur in a mixed anemia (folic acid and iron deficiency). A. MCV is the ratio of the Hct to the RBC count. It essentially assesses average RBC size and reflects any anisocytosis.  Normal values are 14 to 18 g/dL for men and 12 to 16 g/dL for women.  Low Hb values indicate anemia. HCT (OR) PACKED CELL VOLUME (PCV) HEMOGLOBIN
PHARMD GURU Page 3 (1) Low MCV indicates microcytic (undersize) RBCs, as occurs in iron deficiency. (2) High MCV indicates macrocytic (oversize) RBCs, as occurs in a vitamin B12 or folic acid deficiency. (3) Normal range for MCV is 90 ± 10. B. Mean cell hemoglobin (MCH) assesses the amount of Hb in an average RBC. (1) MCH is defined as: (2) Normal range for MCH is 30 ± 4. C. Mean cell hemoglobin concentration (MCHC) represents the average concentration of Hb in an average RBC, defined as: (1) Normal range for MCHC is 34 ± 3. (2)Low MCHC indicates hypochromia (pale RBCs resulting from decreased Hb content), as occurs in iron deficiency. D. Red blood cell distribution width (RDW) is a relatively new index of RBCs. Normally; most RBCs are approximately equal in size, so that only one bell-shaped histogram peak is generated. Disease may change the size of some RBCs - for example, the gradual change in size of newly produced RBCs in folic acid or iron deficiency. The difference in size between the abnormal and the less abnormal RBCs produces either more than one histogram peak or a broadening of the normal peak. This value is used primarily with other tests to diagnose iron deficiency anemia.
PHARMD GURU Page 4 (1) An increased RDW is found in factor deficiency anemia (e.g., iron, folate, vitamin B12). (2) A normal RDW is found in such conditions as anemia or chronic disease. (3) The RDW index is never decreased. 5. The reticulocyte count provides a measure of immature RBCs (reticulocytes), which contain remnants of nuclear material (reticulum). Normal RBCs circulate in the blood for about 1 to 2 days in this form. Hence, this test provides an index of bone marrow production of mature RBCs. a. Reticulocytes normally make up 0.1% to 2.4% of the total RBC count. b. Increased reticulocyte count occurs with such conditions as haemolytic anemia, acute blood loss, and response to the treatment of a factor deficiency (e.g., an iron, vitamin B12, or folate deficiency). Polychromasia (the tendency to stain with acidic or basic dyes) noted on a peripheral smear laboratory report usually indicates increased reticulocytes. c. Decreased reticulocyte count occurs with such conditions as drug-induced aplastic anemia. 6. The erythrocyte sedimentation rate (ESR) measures the rate of RBC settling of whole, uncoagulated blood over time, and it primarily reflects plasma composition. Most of the sedimentation effect results from alterations in plasma proteins. a. Normal ESR rates range from 0 to 20 mm/hr for males and from 0 to 30 mm/hr for females. b. ESR values increase with acute or chronic infection, tissue necrosis or infarction, well established malignancy, and rheumatoid collagen diseases. c. ESR values are used to: RETICULOCYTE COUNT ERYTHROCYTE SEDIMENTATION RATE (ESR)