Hematology and RBC Metabolism Principles

Vocabulary-style practice flashcards covering hematology analyzer principles, RBC indices, cell morphology, hematopoiesis, and hemoglobin metabolism based on the lecture notes.

Sodium lauryl sulfate (SLS) method

A cyanide-free method that lyses RBCs and WBCs to oxidize the heme group, forming a colored compound whose absorbance measured is proportional to the hemoglobin in the sample.

Coulter Principle (Electrical Impedance)

A measurement technique where resistance between two electrodes increases as a non-conducting cell passes through a small aperture, generating an electrical pulse.

Electrical Impedance: Amplitude

The height of the voltage pulse which is derived from and represents the cell size.

Electrical Impedance: Frequency

The number of pulses generated, which represents the cell count.

Electrical Impedance: Thresholds

Values set by the analyzer to differentiate between RBCs, WBCs, and platelets.

Mean Cell Volume (MCV)

A measure of red cell size with a normal range of $80-100\,fL$. It is calculated as \frac{\text{Hct (\%)} \times 10}{\text{RBC count (million/mm^3)}}.

Mean Cell Hemoglobin (MCH)

The mean weight of hemoglobin per erythrocyte, with a normal range of $27-34\,pg$. It is calculated as \frac{\text{Hgb (g/dL)} \times 10}{\text{RBC count (x10^{12}/L)}}.

Mean Cell/Corpuscular Hemoglobin Concentration (MCHC)

Relates the average mass of hemoglobin in RBCs to the average volume of RBCs, with a normal range of $32-36\%$. It is calculated as $\frac{\text{Hgb (g/dL)} \times 100}{\text{Hct (\%)}}$.

RPI (Reticulocyte Production Index)

An index calculated as $\frac{\text{Retic count (\%)} \times (\text{Patient Hct (\%)} / 45\%)}{\text{Retic maturation time}}$.

3-Part WBC Differential

An analyzer report that differentiates only three types of WBCs: Granulocytes (Neutrophils), Monocytes, and Lymphocytes.

5-Part WBC Differential

An analyzer report that differentiates all five types of WBCs: Segmented Neutrophils, Eosinophils, Basophils, Lymphocytes, and Monocytes.

Lipemic specimen interference

Lipemia causes increased turbidity that affects spectrophotometric readings leading to falsely increased HGB and MCH; it is corrected by a saline replacement procedure.

nRBC interference on WBC Histogram

The presence of nucleated red blood cells (nRBCs) can cause an extra peak to the left of the lymphocyte curve, leading to a falsely elevated WBC count.

Mesoblastic Phase

The earliest phase of hematopoiesis beginning around the 19th day of embryonic development, where cells from the mesoderm migrate to the yolk sac.

Hepatic Phase

The phase of hematopoiesis beginning in the 2nd month of gestation where the liver is the major site of production; the thymus also develops as a site for T cell production during this time.

Medullary (Myeloid) Phase

The phase beginning before the 7th month of fetal development where the bone marrow becomes the primary site of hematopoiesis.

Spleen: Culling

A process where the spleen phagocytizes cells and degrades their contents.

Spleen: Pitting

A process where macrophages in the spleen remove cell inclusions or damaged membrane from RBCs without destroying the cell.

Asplenia

The absence of splenic function due to surgery (splenectomy) or autosplenectomy (e.g., in Sickle Cell Anemia), resulting in the presence of inclusions like Howell-Jolly bodies and target cells.

M:E Ratio

The ratio of myeloid precursors to erythroid precursors in the bone marrow; the normal ratio is $3:1$, while CML can show a ratio > 10:1.

Erythropoietin (EPO)

A lineage-specific glycoprotein hormone produced in the kidney that binds to CFU-E receptors to stimulate maturation and prevent apoptosis of erythroid progenitors.

Spectrin

The peripheral protein of the red cell membrane primarily responsible for red cell deformability; loss of ATP leads to decreased phosphorylation of this protein.

Anisocytosis

Variation in red cell size, which correlates with the RDW (Red Cell Distribution Width) parameter.

Poikilocytosis

A general term for variations in red cell shape.

Codocytes

The alternate name for target cells, which are bell-shaped cells with excess membrane cholesterol/phospholipid often seen in liver disease or post-splenectomy.

Drepanocytes

The alternate name for sickle cells, caused by the polymerization of hemoglobin S under low oxygen tension.

Dacryocytes

The alternate name for tear drop cells, often associated with IMF, IDA, or Thalassemia.

Microcytes

RBCs with a diameter < 6\,\mu m, commonly seen in IDA, Thalassemia, and lead poisoning.

Macrocytes

RBCs with a diameter > 8\,\mu m, commonly seen in megaloblastic anemia, liver disease, and high reticulocyte counts.

Howell-Jolly Bodies

Nuclear remnants containing DNA that appear as single or double 1 to $2\,\mu m$ inclusions along the RBC periphery, common in post-splenectomy.

Basophilic Stippling

RBC inclusions composed of ribosomes, ribonucleoprotein, and mitochondrial remnants, strongly associated with lead poisoning.

Heinz Bodies

Inclusions visualized as 'bite cells' or helmet cells due to the pitting mechanism of the spleen; associated with G6PD deficiency.

Pappenheimer Bodies

Siderotic granules containing nonheme iron that appear in clusters along the periphery of RBCs on a Wright stain.

ALA synthase

The enzyme responsible for the first, rate-limiting step of heme synthesis, converting glycine and succinyl CoA into ALA in the mitochondria.

Ferrochelatase

The enzyme used in the final step of heme synthesis to convert protoporphyrin IX and $Fe^{2+}$ into heme.

Bohr effect

The decrease in hemoglobin's oxygen affinity in response to lowered blood pH resulting from increased $CO_2$ concentration.

P50

The partial pressure of oxygen at which hemoglobin is $50\%$ saturated; normal value is $26.7\,mm\,Hg$.

Carboxyhemoglobin

Hemoglobin bound to carbon monoxide (CO), which has 240 times the affinity of oxygen; leads to a leftward shift in the dissociation curve.

Methemoglobin

Hemoglobin containing iron in the ferric state ($Fe^{3+}$) instead of the ferrous state ($Fe^{2+}$); it cannot carry oxygen and may give blood a brown color.

Sulfhemoglobin

An irreversible form of hemoglobin caused by exposure to sulfur chemicals; it gives blood a green color and cannot be converted back to Hemoglobin A.

Haptoglobin

A protein that binds free hemoglobin (alpha and beta dimers) in the plasma during fragmentation (intravascular) hemolysis.

Hemopexin

A protein that binds methemoglobin in the plasma once haptoglobin is depleted during intravascular hemolysis.

Rh null syndrome

A condition specifically associated with the presence of stomatocytes on a peripheral blood smear.