Erythrocytes Flashcards
Manual RBC counts usage
Rarely done due to inaccuracy; better alternatives like microhematocrit and hemoglobin concentration are preferred.
Effect of high altitude on RBC count
Elevated, with ~1 g Hb/dL increase at 2 km altitude and ~2 g Hb/dL increase at 3 km altitude.
RBC count reference range for children (8-13 y.o.)
4.00 to 5.40 X 10^6/µL or 4.00 to 5.40 X 10^12/L.
RBC count reference range for adult males
4.60 to 6.00 X 10^6/µL or 4.60 to 6.00 X 10^12/L.
RBC count reference range for adult females
4.00 to 5.40 X 10^6/µL or 4.00 to 5.40 X 10^12/L.
ATP role in RBCs
Maintains RBC shape and deformability, provides energy for active cation transport, modulates 2,3-BPG levels.
Major glycolytic pathway in RBCs
Embden-Meyerhof Pathway.
Glucose entry mechanism in RBCs
Via GLUT-1, no energy expenditure.
Percentage of glucose utilization handled by Embden-Meyerhof Pathway
90%.
Type of pathway EMP
Non-oxidative, anaerobic.
ATP production by Embden-Meyerhof Pathway
Produces 2 ATP molecules.
Inheritance pattern of PK deficiency
Autosomal recessive.
Most common enzyme deficiency in EMP
Pyruvate kinase (PK).
Common hereditary anemia linked to PK deficiency
Hereditary nonspherocytic hemolytic anemia (HNSHA).
Peripheral blood smear findings in PK deficiency
Acanthocytes, Burr cells.
Recommended screening test for PK deficiency
PK fluorescent spot test.
Another screening test for PK deficiency
Autohemolysis test.
Confirmatory test for PK deficiency
Quantitative PK assay.
Autohemolysis pattern in PK deficiency
Greatly increased autohemolysis; glucose has no effect, ATP corrects hemolysis (TYPE II).
Alternate pathways of glycolysis
Hexose Monophosphate Shunt, Rapoport-Luebering Shunt, Methemoglobin Reductase Pathway.
Alternate name for Hexose Monophosphate Shunt (HMS)
Pentose phosphate pathway or phosphogluconate pathway.
Primary function of HMS
Converts glucose to pentose and produces NADPH.
Role of NADPH in HMS
Reduces glutathione.
Function of reduced glutathione
Reduces peroxides, protects proteins, lipids, and heme iron from oxidation.
HMS dependence for functionality
Glucose-6-phosphate dehydrogenase (G6PD).
Purpose of HMS in globulin maintenance
Prevents denaturation by oxidation.
Disorder inheritance of G6PD deficiency
X-linked recessive.
Most common enzyme deficiency globally
Glucose-6-phosphate dehydrogenase (G6PD) deficiency.
PBS findings in G6PD deficiency
Heinz bodies, Bite cells.
Screening tests for G6PD deficiency
G6PD fluorescent spot test, Autohemolysis test.
Confirmatory test for G6PD deficiency
Quantitative G6PD test.
Autohemolysis pattern in G6PD deficiency
Slight to moderate increase, partially corrected by glucose (Type I).
WHO Class I G6PD deficiency enzyme activity
Severely deficient (<1% or not detectable).
Clinical manifestation of Class I G6PD deficiency
Chronic hereditary nonspherocytic hemolytic anemia (HNSHA).
Examples of Class I G6PD variants
G6PD-Serres, G6PD-Madrid.
WHO Class II G6PD deficiency enzyme activity
Severely deficient (<10% activity).
Clinical manifestation of Class II G6PD deficiency
Severe, episodic acute hemolytic anemia associated with infections, certain drugs, and fava beans; not self-limited and may require transfusions during hemolytic episodes.
Examples of Class II G6PD variants
G6PD-Mediterranean, G6PD-Chatham.
WHO Class III G6PD deficiency enzyme activity
Mild to moderately deficient (10% to 60% activity).
Clinical manifestation of Class III G6PD deficiency
Episodic, acute hemolytic anemia associated with infections and certain drugs; self-limited.
Examples of Class III G6PD variants
G6PD-A-, G6PD-Canton.
WHO Class IV G6PD deficiency enzyme activity
Mildly deficient to normal (60% to 150% activity).
Clinical manifestation of Class IV G6PD deficiency
None.
Examples of Class IV G6PD variants
G6PD-B (wildtype), G6PD-A+ (may also manifest as Class III).
WHO Class V G6PD deficiency enzyme activity
Increased (>150% activity).
Clinical manifestation of Class V G6PD deficiency
None.
Examples of drugs causing hemolysis in G6PD deficiency
Dapsone, Methylthioninium chloride (methylene blue), Nitrofurantoin, Phenazopyridine, Primaquine, Rasburicase, Tolonium chloride (toluidine blue).
Examples of chemicals causing hemolysis in G6PD deficiency
Aniline dyes, Naphthalene (mothballs).
Foods that may cause hemolysis in G6PD deficiency
Fava beans, Red wine, Legumes (garbanzos, kadyos, munggo), Blueberry, Soya food (taho, tokwa, soy sauce), Ampalaya (bitter gourd).
Common household items to avoid in G6PD deficiency
Menthol (Efficascent Oil, Listerine mouthwash).
Frequently encountered enzymopathies
G6PD deficiency, Pyruvate kinase deficiency.
Other RBC enzymopathies
Rare.
Methemoglobin Reductase Pathway enzyme
Cytochrome b5 reductase.
Function of cytochrome b5 reductase
Maintain iron in the heme in its reduced state (Fe+2).
Rapoport-Luebering Shunt enzyme
2,3-BPG.
Function of 2,3-BPG
Binds to hemoglobin and decreases its oxygen affinity.
Factors affecting oxygen dissociation from hemoglobin
Partial pressure of oxygen, Affinity of hemoglobin for oxygen.
Factors affecting hemoglobin affinity for oxygen
pH, Partial pressure of carbon dioxide, Concentration of 2,3-BPG, Temperature, Presence of other nonfunctional hemoglobin species.
What does the Oxygen Dissociation Curve represent?
The relationship between oxygen saturation of hemoglobin and the partial pressure of oxygen, plotted on a graph.
Increased affinity (Shift to the left)
Increased pH, decreased PCO2, decreased 2,3-BPG, decreased temperature.
Decreased affinity (Shift to the right)
Decreased pH, increased PCO2, increased 2,3-BPG, increased temperature.
Bohr effect
A shift in the curve due to an alteration in pH (or hydrogen ion concentration) and the effect of hydrogen ions and CO2 on the affinity of hemoglobin for oxygen.
Haldane effect
Occurrence where the binding of O2 to hemoglobin promotes the release of CO2.
