Sickle Cell

Genetics Review Chromosomes Genes Loci Genotype

Normal Adult Hemoglobin (Hgb A) Heme molecule composed of iron in the ferrous state (Fe++) Globin is the protein portion 95-98% of adult Hgb is Hgb A Remaining amount is A2 and A3

Sickle Cell Hemoglobin (Hgb S) The amino acid glutamic acid is replaced by amino acid valine Ability of RBCs oxygen carrying capability is impaired Two possible genotype AS (sickle cell trait) SS (sickle cell disease)

Pathophysiology of Sickle Cell Sickle Cell trait Clinical manifestation Sickle Cell disease

Peripheral Blood Picture Varying number of sickled forms Marked anisocytosis, poikilocytosis, and polychromasia Target cells, nucleated RBCs, increased WBCs and platelets Reticulocyte count is elevated: (5-25%)

Sodium metabisulfite Principle Cells containing Hgb S will “sickle” when placed under a condition of reduced oxygen tension Sodium Metabisulfate 15 minutes & 30 minutes

Dithionite tube test Principle Hgb S is insoluble in a phosphate buffer Results in turbidity Hgb A is soluble Results in clear appearance Other abnormal hemoglobins may result in turbidity

ESR Clinical Significance The ESR is a nonspecific test that suggests the possibility of an inflammatory process or tissue damage in the body The ESR is not diagnostic but is useful in following the course of some diseases like rheumatic fever, arthritis, and Lupus

Principle Based on principle of sedimentation where solids settle to the bottom of a liquid A known quantity of anticoagulated blood is left undisturbed, the RBCs separate from the plasma and fall to the bottom of the container

Procedure Anticoagulated blood is placed in a calibrated tube of standard dimensions It is incubated in a vertical position and left undisturbed for a designated period of time (usually 1 hr) Distance RBCs fall within the given time is measured in millimeters and reported mm/hr

Types of ESR Methods Wintrobe – simplest and mostcost effective Westergren – more sensitive Automated methods

Factors affecting ESR Plasma factors Abnormal plasma proteins may lead to rouleaux formation (falsely increases ESR) The single most important factor in determining ESR rate

RBC Factors Size Shape Number of RBCs Large erythrocytes settle faster than smaller ones and will increase ESR Shape spherocytes settle rapidly while sickle cells settle very slowly Number of RBCs In anemia there are less RBCs and more plasma volume which increases ESR

Technical Factors Tilting Noise and vibration Temperature Test set up within 2hrs of blood collection ESR tube Well mixed sample Air bubbles Accurately timed This project was funded at $3,000,000 (100% of its total cost) from a grant awarded under the Trade Adjustment Assistance Community College and Career Training Grants, as implemented by the U.S. Department of Labor’s Employment and Training Administration. Rogue Community College is an equal opportunity employer/program. Auxiliary aids and services, alternate form and language services are available to individuals with disabilities and limited English proficiency free of cost upon request.   This work is licensed under a Creative Commons Attribution 4.0 International License.