(BQ) Part 2 book "Essentials of clinical pathology" presentation of content: Estimation of hemoglobin, total leukocyte count, red cell indices, laboratory tests in anemia, laboratory tests in hematological malignancies, erythrocyte sedimentation rate,. and other contents. | 18 Estimation of Hemoglobin Hemoglobin carries oxygen from the lungs to the tissues and carbon dioxide from tissues to the lungs. It is composed of heme (iron + protoporphyrin) and globin polypeptide chains. Hemoglobin is not homogeneous and normally different variants and derivatives exist. Normal hemoglobin variants are embryonic hemoglobins (Gower I, Gower II, and Portland), fetal hemoglobin (Hb F), adult hemoglobin (Hb A), and Hb differ from each other in the type of polypeptide chains (Box ). INDICATIONS FOR HEMOGLOBIN ESTIMATION 1. To determine presence and severity of anemia: Anemia refers to low hemoglobin concentration or oxygen-carrying capacity of blood. Clinical signs of anemia (pallor of skin, conjunctival vessels, or mucous membranes) are unreliable for diagnosis of anemia. Anemia is best assessed by estimation of hemoglobin or packed cell volume (See Chapter 27: Laboratory Tests in Anemia). Box : Hemoglobin • Normal physiological hemoglobins: Oxyhemoglobin, Reduced hemoglobin (. iron of heme not associated with oxygen) • Hemoglobin derivatives: Compounds formed from physiological hemoglobins through the action of acids, alkalis, oxidizing/reducing agents, etc. They are identified by their characteristic absorption spectra in a spectrophotometer. • Hemoglobin variants: Different structural forms of hemoglobin that differ in structure of polypeptide chains. They are identified by hemoglobin electrophoresis. – Normal: HbA (α2β2), HbF (α2γ2), HbA2 (α2δ2) – Abnormal: HbS, HbC, HbD, HbE, etc. Box : Polycythemia • Primary: Increase in total red cell mass with low erythropoietin level . polycythemia vera • Secondary: Increase in total red cell mass with increased erythropoietin level, . hypoxia • Relative: Decrease in plasma volume with red cell mass remaining normal, . dehydration. 2. Screening for polycythemia: Polycythemia refers to increased hemoglobin level above the normal range. It may be primary, secondary, or .
