Midterm

What are the adult reference ranges for total white blood cells ($\text{WBC}$) and each of the five differential leukocyte types?

Total $\text{WBC} = 4.8\text{--}10.8 \times 10^9/\text{L}$, Neutrophils = $2.0\text{--}7.5 \times 10^9/\text{L}$, Lymphocytes = $1.2\text{--}3.4 \times 10^9/\text{L}$, Monocytes = $0.1\text{--}0.9 \times 10^9/\text{L}$, Eosinophils = $0\text{--}0.6 \times 10^9/\text{L}$, and Basophils = $0\text{--}0.2 \times 10^9/\text{L}$.

What are the normal percentage distributions of circulating T cells, NK cells, and B cells within the lymphocyte population?

T cells: $60\text{--}80\%$, NK cells: $<20\%$, and B cells: $10\text{--}20\%$.

During an inflammatory response to a pathogen, how long does the bone marrow take to increase neutrophil production and release band forms into the peripheral blood film ($\text{PBF}$)?

It takes up to $24\,\text{hours}$ to increase production of neutrophils, at which point band neutrophils become noticeable on the $\text{PBF}$.

What quantitative criterion defines a significant neutrophil "left shift" in peripheral blood?

An absolute band neutrophil count of $> 0.7 \times 10^9/\text{L}$, or when band cells are accompanied by earlier immature granulocytic stages.

How are band neutrophils recorded on laboratory differential forms and incorporated into the Absolute Neutrophil Count ($\text{ANC}$)?

Band cells are counted separately to monitor for a left shift, but their count is added back into the mature neutrophil count to calculate the total $\text{ANC}$.

What are toxic granulation and toxic vacuolization in neutrophils, and what do they signify?

Toxic granulation consists of larger, darker mutated primary granules composed primarily of peroxidase. Toxic vacuolization represents cytoplasmic vacuoles formed by phagocytosis and digestion of foreign particles. Both are classic signs of bacterial infection.

What are Döhle bodies, where are they located within the cell, and what is their ultrastructural composition?

Döhle bodies are light blue-gray cytoplasmic inclusions located near the periphery of neutrophils. They represent remnants of ribosomal RNA ($\text{rRNA}$) or rough endoplasmic reticulum ($\text{rER}$) resulting from accelerated granulopoiesis.

Which white blood cell lines are selectively infected by Ehrlichia chaffeensis and Anaplasma phagocytophilum, and how are these infections definitively distinguished?

Ehrlichia chaffeensis infects monocytes (Ehrlichiosis), whereas Anaplasma phagocytophilum infects neutrophils (Anaplasmosis). They are differentiated definitively using polymerase chain reaction ($\text{PCR}$).

What are the absolute count thresholds defining neutrophilia and neutropenia?

Neutrophilia: Absolute neutrophil count $> 7.5 \times 10^9/\text{L}$. Neutropenia: Absolute neutrophil count $< 2.0 \times 10^9/\text{L}$.

What are the "Alert" and "Critical" absolute count thresholds for neutrophilia and neutropenia?

Neutrophilia Alert: $> 50.0 \times 10^9/\text{L}$, Critical: $> 100 \times 10^9/\text{L}$. Neutropenia Alert: $< 1.0 \times 10^9/\text{L}$, Critical: $< 0.5 \times 10^9/\text{L}$.

What are "green crystals of death" (death crystals) in neutrophils and monocytes, and what clinical conditions do they indicate?

They are green cytoplasmic inclusions seen in advanced liver failure, multiple organ failure, and severe COVID-19 infection, typically associated with elevated $\text{LDH}$, marked tissue injury, hemolysis (high bilirubin), and elevated lactic acid.

What causes iso-immune (allo-immune) neutropenia in newborns, and how is moderate to marked disease treated?

It is caused by maternal $\text{IgG}$ antibodies produced against fetal neutrophil antigens that cross the placenta and destroy fetal neutrophils. Moderate to marked disease is treated with glucocorticosteroids and immunoglobulin CSF.

What is Pelger-Huët Anomaly ($\text{PHA}$), what is its inheritance pattern, and how does pseudo-Pelger-Huët differ?

Pelger-Huët Anomaly is an autosomal dominant condition characterized by hyposegmented, bilobed ("pince-nez") neutrophil nuclei joined by a fine filament. Pseudo-Pelger-Huët anomaly exhibits "pince-nez" nuclei in $< 30\%$ of neutrophils and is associated with myelodysplastic syndrome ($\text{MDS}$).

What triad of hematologic features characterizes May-Hegglin Anomaly ($\text{MYH9}$ disorder)?

Abnormally large hypogranular platelets (giant platelets/"ghost cells"), thrombocytopenia with bleeding risk, and Döhle-like inclusion bodies in neutrophils and other granulocytes.

What is Alder-Reilly Anomaly ($\text{ARA}$), and how are its inclusions distinguished from toxic granulation?

Alder-Reilly Anomaly is an autosomal recessive disorder featuring large, dark purple-staining inclusions ("Reilly bodies") found in clusters across neutrophils, monocytes, and lymphocytes. The cells maintain normal function.

What clinical and cellular abnormalities characterize Chédiak-Higashi Anomaly?

An autosomal recessive immunodeficiency characterized by partial albinism, photosensitivity, nystagmus, recurrent infections, neutropenia, bleeding tendencies, and giant dark purple/reddish lysosomal granules in white blood cells.

What are the tissue and blood circulation lifespans of human eosinophils?

Eosinophils survive for $8\text{--}12\,\text{days}$ in tissue, but circulate in the peripheral blood for only $8\text{--}12\,\text{hours}$.

What are "Harlequin cells" and in what clinical conditions are they observed?

Harlequin cells are dysplastic eosinophils containing atypical basophilic-staining granules alongside eosinophilic granules, most commonly observed in chronic myeloid leukemia ($\text{CML}$) or myelodysplastic syndrome ($\text{MDS}$).

What chemical substances are stored in the granules of basophils?

Histamine (increases localized blood flow), heparin (anticoagulant), proteolytic enzymes (such as peroxidase), and serotonin.

What is the threshold for reporting reactive lymphocytes on a peripheral blood differential, and why are terms like "atypical" or "variant" no longer recommended?

Reactive lymphocytes are reported when they exceed $> 5\%$ of lymphocytes. Terms such as "atypical" are discontinued because "atypical" implies a malignant or premalignant process, whereas reactive lymphocytes are functionally normal cells responding to an antigenic stimulus.

What are Mott cells, and what do they contain?

Mott cells are atypical plasma cells filled with multiple Russell bodies, which are globular endoplasmic reticulum inclusions packed with accumulated immunoglobulins.

What are smudge cells (basket cells), what is their reporting threshold in $\text{CLL}$, and how are they eliminated for differential counting?

Smudge cells are fragile lymphoid artifacts ruptured during smear preparation. If smudge cells constitute $> 10\%$ of $\text{WBCs}$, add them into the lymphocyte count and report "smudge cells present". They can be eliminated by adding $1\,\text{drop}$ of $22\%$ bovine albumin to $4\text{--}5\,\text{drops}$ of blood and remaking the smear.

What principle governs the classic Monospot latex agglutination test for infectious mononucleosis ($\text{IM}$), and what causes false-positive reactions?

It detects heterophile $\text{IgM}$ antibodies in patient serum that agglutinate polystyrene latex beads coated with Paul-Bunnell antigen (derived from sheep/horse $\text{RBCs}$). False positives are caused by rheumatoid factor ($\text{IgM}$ anti-$\text{IgG}$), polyclonal $\text{IgM}$, autoimmune diseases, lymphoid malignancies, and hypergammaglobulinemia.

In Sysmex flow cell analysis, what physical properties of leukocytes are measured by Forward Scatter ($\text{FSC}$), Side Scatter ($\text{SSC}$), and Side Fluorescence Light ($\text{SFL}$)?

Forward Scatter ($\text{FSC}$) measures cell volume/size; Side Scatter ($\text{SSC}$) measures internal cell complexity and granularity; Side Fluorescence Light ($\text{SFL}$) measures $\text{DNA}$ and $\text{RNA}$ content via fluorochrome dye binding.

On this Sysmex flow cytometry scattergram ($\text{SFL}$ vs $\text{SSC}$), which leukocyte population is located at the region with high granularity ($\text{SSC}$) but low-to-intermediate fluorescence ($\text{SFL}$)?

The Neutrophil + Basophil ($\text{NEUT+BASO}$) population, positioned to the right of lymphocytes due to greater granularity.

Which automated complete blood count parameters are known to artificially increase versus decrease as a blood sample ages?

Parameters that increase: $\text{HCT}$, $\text{MCV}$, $\text{RDW-SD}$, $\text{PLT-O}$, and $\text{PLT-F}$. Parameters that decrease: Monocytes, Immature Granulocytes ($\text{IG}$), Reticulocytes ($\text{Ret}$), Immature Reticulocyte Fraction ($\text{IRF}$), and Hematopoietic Progenitor Cells ($\text{HPC}$).

What are the maximum allowable limits for automated analyzer background count readings for $\text{WBC}$, $\text{RBC}$, $\text{HGB}$, and $\text{PLT}$?

$\text{WBC} \le 0.1 \times 10^9/\text{L}$, Diff $\text{WBC} \le 0.2 \times 10^9/\text{L}$, $\text{RBC} \le 0.02 \times 10^{12}/\text{L}$, $\text{HGB} \le 1\,\text{g/dL}$, and $\text{PLT} \le 5 \times 10^9/\text{L}$ ($\text{PLT-O} \le 10 \times 10^9/\text{L}$).

What are the three analytical components of Beckman Coulter's $\text{VCS}$ technology?

$\text{V}$ = Volume (low-frequency direct current impedance to measure physical cell size); $\text{C}$ = Conductivity (high-frequency radiofrequency current that penetrates cell membranes to assess nuclear density and internal composition); $\text{S}$ = Light Scatter (multi-angle light scatter assessing cytoplasmic granularity, nuclear lobularity, and surface structure).

How does the Siemens ADVIA system differentiate basophils in its dedicated Baso/Lobularity channel?

An acidic surfactant lyses and strips the cytoplasm and membranes of all white blood cells except basophils, which are lyse-resistant; intact basophils are then quantified by their high low-angle scatter.

What is a delta check in laboratory hematology, which Complete Blood Count parameter is most stable for it, and what represents the most common cause of a delta flag?

A delta check is an automated alert triggered when a current patient result differs from their prior result by more than a predefined threshold. $\text{MCV}$ is the most stable parameter. The number one cause of delta check flags is pre-analytical error (such as mislabeled specimen or IV contamination).

How do Acanthocytes and Echinocytes differ in their morphological appearance and underlying mechanism of formation?

Acanthocytes (spur cells) have irregularly spaced, variable-length pointed projections with no central pallor, caused by altered membrane lipid proportions. Echinocytes (burr cells) possess $10\text{--}30$ blunt, evenly spaced projections while retaining central pallor, caused by alterations in extracellular pH, low albumin, or uremia.

What are schistocytes, how do they form, and what life-threatening conditions are associated with their presence alongside thrombocytopenia?

Schistocytes are fragmented red blood cells with sharp angles/points formed by mechanical shearing against fibrin strands in microcirculation or prosthetic heart valves. Alongside thrombocytopenia, they indicate microangiopathic hemolytic anemia ($\text{MAHA}$), including $\text{DIC}$, $\text{TTP}$, $\text{HUS}$, and $\text{HELLP}$ syndrome.

Under what blood smear condition must a sample showing platelet clumping be rejected and recollected?

When platelet clumps are accompanied by visible fibrin strands, indicating in vitro specimen clotting; if no clotting/fibrin is present, the $\text{PLT}$ count is withheld while remaining $\text{CBC}$ parameters may be acceptable.

What causes platelet satellitism on peripheral blood films, and how does it impact automated testing?

It is an in vitro artifact caused by $\text{EDTA}$-dependent antibodies binding platelets to the surface of neutrophils. It causes falsely decreased automated platelet counts and invalidates impedance $\text{WBC}$ counts.

What cell type and structural remnant is demonstrated by supravital staining (e.g., New Methylene Blue) in this image, and what is its adult reference range?

Reticulocytes containing precipitated ribosomal $\text{RNA}$ fragments. The reference range is $0.5\text{--}2.0\%$ or $24\text{--}84 \times 10^9/\text{L}$.

What morphological category of red blood cells is illustrated by this progression showing progressive enlargement of central pallor?

Hypochromic red blood cells progressing from normal red blood cell to hypochromic $\text{RBC}$ to severe hypochromia (decreased intracellular hemoglobin concentration).

What five conditions comprise the "TAILS" differential diagnosis for hypochromic microcytic anemia?

Thalassemia, Anemia of chronic disease/inflammation ($\text{ACI}$), Iron deficiency anemia ($\text{IDA}$), Lead poisoning, and Sideroblastic anemia ($\text{SA}$).

What is the Mentzer Index formula, and what cutoff values differentiate Thalassemia trait from Iron Deficiency Anemia?

$\text{Mentzer Index} = \frac{\text{MCV}\,(\text{fL})}{\text{RBC}\,(10^{12}/\text{L})}$. A value $< 13$ suggests Thalassemia trait, whereas a value $> 13$ suggests Iron Deficiency Anemia.

How does hepcidin regulate systemic iron absorption in normal versus inflammatory states?

Hepcidin inhibits intestinal iron absorption and macrophage iron release. In normal homeostasis, high iron stimulates hepcidin ($\downarrow$ absorption) and low iron inhibits hepcidin ($\uparrow$ absorption). In chronic inflammation, persistent $\text{IL-6}$ elevation drives high hepcidin levels regardless of iron status, trapping iron inside macrophages.

How do serum iron, Total Iron Binding Capacity ($\text{TIBC}$), serum ferritin, and transferrin saturation differ between Iron Deficiency Anemia ($\text{IDA}$) and Anemia of Chronic Inflammation ($\text{ACI}$)?

$\text{IDA}$: low serum iron, elevated $\text{TIBC}$, low ferritin, and low percent saturation. $\text{ACI}$: low serum iron, low $\text{TIBC}$, normal to elevated ferritin, and normal to low percent saturation.

What is the defining bone marrow finding of Sideroblastic Anemia on a Prussian blue stain?

Ringed sideroblasts, which are erythroid precursors showing iron accumulation within mitochondria forming a collar or ring around the nucleus.

What are the molecular structure and clinical presentation of Beta-Thalassemia Major (Cooley's anemia)?

Homozygous absence of both beta-globin genes, resulting in severe hemolytic anemia in infants, absent $\text{HbA}$, marked elevation of $\text{HbF}$ ($95\text{--}98\%$), hepatosplenomegaly, skeletal deformities, and transfusion dependency.

What abnormal hemoglobin inclusion body is depicted here, what globin chains comprise it, and in what disorder is it observed?

Hemoglobin H ($\text{HbH}$) inclusion bodies, representing unstable tetramers of four beta chains ($\beta_4$) with a "golf-ball" appearance under supravital staining, seen in Alpha-Thalassemia Intermedia ($\text{HbH}$ disease).

What are the globin chain compositions of Hemoglobin Barts and Hemoglobin H, and which forms of alpha thalassemia produce them?

$\text{Hb Barts}$ is a tetramer of four gamma chains ($\gamma_4$), occurring in homozygous alpha thalassemia major ($--/--$, Hydrops Fetalis). $\text{HbH}$ is a tetramer of four beta chains ($\beta_4$), occurring when three alpha genes are deleted ($--/-A$, $\text{HbH}$ disease).

On cellulose acetate hemoglobin electrophoresis at alkaline $\text{pH}\ 8.4$, what is the migration order of standard hemoglobins from the cathode ($-$) to the anode ($+$)?

Cathode ($-$) Origin $\rightarrow \text{HbC} \rightarrow \text{HbS} \rightarrow \text{HbF} \rightarrow \text{HbA}$ Anode ($+$) (often remembered by the mnemonic "Crawl, Slow, Fast, Accelerate").

What genetic mutations and clinical complications define Hereditary Hemochromatosis ($\text{HH}$)?

An autosomal recessive disorder associated with $\text{C282Y}$ and $\text{H63D}$ mutations, causing impaired hepcidin regulation, hyperabsorption of dietary iron, elevated transferrin saturation, and organ toxicity (liver cirrhosis, cardiac arrhythmias, diabetes, and hyperpigmentation).

What hematologic features define Megaloblastic Macrocytic Anemia on peripheral blood smear and bone marrow evaluation?

Oval macrocytes ($\text{MCV} > 100\,\text{fL}$, often $> 110\,\text{fL}$), hypersegmented neutrophils ($\ge 5$ lobes in multiple cells or $\ge 1$ neutrophil with $\ge 6$ lobes), pancytopenia, marked anisopoikilocytosis, and bone marrow nuclear-cytoplasmic asynchrony with megaloblasts.

How do serum Methylmalonic Acid ($\text{MMA}$) and Homocysteine levels differentiate Vitamin $\text{B}_{12}$ deficiency from Folate deficiency?

Vitamin $\text{B}_{12}$ deficiency presents with elevated $\text{MMA}$ and elevated homocysteine. Folate deficiency presents with elevated homocysteine but normal $\text{MMA}$.

What distinguishes non-megaloblastic macrocytosis (e.g., in liver disease or alcoholism) from megaloblastic anemia?

Non-megaloblastic macrocytosis features round macrocytes rather than oval macrocytes, lacks hypersegmented neutrophils, displays normal bone marrow maturation, and exhibits normal vitamin $\text{B}_{12}$ and folate levels.

What abnormal laboratory pattern identifies Cold Agglutinin Disease (pseudo-macrocytosis), and what corrective procedure should be initiated?

Markedly elevated $\text{MCHC} > 360\,\text{g/L}$, falsely elevated $\text{MCV}$, and falsely low $\text{RBC}$ count. The sample must be incubated at $37^\circ\text{C}$ for $20\text{--}30\,\text{minutes}$ and rerun warm; if unresolved, perform a warm plasma replacement with isotonic diluent.