White Blood Cell Differential Count

Comprehensive review flashcards covering Module 11: White Blood Cell Differential Count from the University of San Agustin - Iloilo College of Pharmacy and Medical Technology.

What is the normal reference range for the total white blood cell (WBC) count in peripheral blood?

$$4500\text{--}11,500/\mu\text{L}$$

How are leukopenia and leukocytosis defined based on WBC count thresholds?

Leukopenia is defined as a low WBC count ($<4,500/\mu\text{L}$), and leukocytosis is defined as a high WBC count ($>11,500/\mu\text{L}$).

What staining technique and microscopy are required to evaluate and differentiate WBC categories on a peripheral blood smear?

Light microscopy using a Wright-stained blood film (under Romanowsky stain).

What are the two major morphological categories of white blood cells, and which cell types belong to each?

Granulocytes (Neutrophil, Eosinophil, and Basophil) and Mononuclear Cells (Monocyte and Lymphocyte).

What types of granules can be present within the cytoplasm of granulocytes?

Primary non-specific azurophilic granules, secondary specific granules, and tertiary or secretory granules.

What is the primary function and other common names for segmented neutrophils?

They are phagocytic cells whose purpose is to engulf and destroy microorganisms and foreign material; they are also known as NEUTs, SEGs, polymorphonuclear neutrophils, and PMNs.

What are the typical size and cytoplasmic staining characteristics of a mature segmented neutrophil?

Size is $9\text{--}15\,\mu\text{m}$ in diameter, containing an abundant amount of pink to rose-violet specific granules (violet due to neutral pH).

What absolute neutrophil count (ANC) thresholds define neutrophilia in adults and children?

Above $7.0 \times 10^9/\text{L}$ in adults, and above $8.5 \times 10^9/\text{L}$ in children.

What absolute neutrophil count (ANC) values define neutropenia in White adults compared to Black adults?

Below $2.0 \times 10^9/\text{L}$ in White adults, and below $1.3 \times 10^9/\text{L}$ in Black adults.

What defines a hypersegmented neutrophil, and what are its primary causes?

A neutrophil possessing $6$ or more nuclear lobes; most commonly seen in megaloblastic anemia due to Vitamin B12 or folic acid deficiency, as well as myelodysplastic syndromes and rare congenital conditions.

What specific abnormal neutrophil is indicated by the yellow arrow in this peripheral blood smear?

Hypersegmented neutrophil

What are the distinctive nuclear and cytoplasmic characteristics of a neutrophil band cell?

Size is $9\text{--}15\,\mu\text{m}$ in diameter with abundant pink to rose-violet granules, and an unsegmented nucleus shaped like a rod, horse shoe, curved link of sausage, or band (nuclear indentation greater than $1/2$ diameter).

What is meant by the hematological term 'left shift'?

An increase in band neutrophils signaling a bacterial infection, caused by the bone marrow accelerating neutrophil production and release to combat bacteria.

What immature granulocyte stage is indicated by the yellow arrow in this smear?

Band neutrophil (Band cell)

What are the key morphological features of an eosinophil regarding granules and nuclear lobes?

Size is $9\text{--}15\,\mu\text{m}$ in diameter, with a full complement of large, bright orange-red cytoplasmic granules and a nucleus that usually possesses two lobes with a coarse, clumped chromatin pattern.

What absolute eosinophil count defines eosinophilia, and which cytokines primarily stimulate it in nonmalignant conditions?

An absolute eosinophil count $>0.4 \times 10^9/\text{L}$, stimulated primarily by interleukin-3 ($\text{IL-3}$) and interleukin-5 ($\text{IL-5}$) during allergic reactions or parasitic infections.

What absolute count defines eosinopenia, and under what circumstances does it commonly occur?

An absolute count $<0.09 \times 10^9/\text{L}$; commonly occurs in leukocyte marrow hypoplasia or during acute infections/inflammations with neutrophilia where eosinophils migrate into tissues.

Identify the specific type of white blood cell indicated by the yellow arrow.

Eosinophil

What are the structural features and staining behavior of basophil granules?

They are dark purple or blue-black specific granules containing histamines and other proteins; they are water-soluble and tend to wash out during staining, often obscuring the nucleus.

What threshold defines basophilia, and what clinical significance does it have?

An absolute basophil count of $>0.15 \times 10^9/\text{L}$; it is rare and frequently signals a hematologic disease.

What is the primary malignant cause of basophilia, and what are several non-malignant causes?

Malignant: Chronic myelogenous leukemia. Non-malignant: allergic rhinitis, hypersensitivity to drugs or food, chronic infections, hypothyroidism, chronic inflammatory conditions, radiation therapy, and bee stings.

Identify the leukocyte indicated by the yellow arrow in this blood film.

Basophil

How do the nuclei of mononuclear cells differ from those of granulocytes?

Mononuclear cells have non-segmented nuclei (round, oval, indented, or folded) without connecting filaments.

What are the characteristic size, cytoplasm, and nuclear chromatin features of normal lymphocytes?

Size is $8\text{--}10\,\mu\text{m}$ in diameter with a thin rim of moderate to dark blue nongranular cytoplasm, and a dense, clumped chromatin pattern described as 'soccer' or 'tortoise shell' chromatin.

What absolute lymphocyte counts define lymphocytosis in children and adults?

Above $10.0 \times 10^9/\text{L}$ in children, and above $4.5 \times 10^9/\text{L}$ in adults.

What absolute lymphocyte counts define lymphocytopenia in children and adults?

Below $2.0 \times 10^9/\text{L}$ in children, and below $1.0 \times 10^9/\text{L}$ in adults.

Identify the mononuclear leukocyte pointed out by the yellow arrow in this field.

Lymphocyte

What is a monocyte, and what distinction does it hold among mature peripheral blood cells?

It is an immature macrophage migrating from the bone marrow to tissues; it is considered the largest cell in normal peripheral blood ('Biggest Mature WBC'), measuring $14\text{--}20\,\mu\text{m}$ in diameter.

What does the cytoplasm and nucleus of a monocyte look like on a Wright-stained smear?

Abundant blue-gray cytoplasm with fine azurophilic granules ('ground glass' appearance) and occasional vacuoles; the nucleus is round, kidney-shaped, horseshoe, or tulip-shaped.

What absolute monocyte counts define monocytosis in neonates and adults?

Above $3.5 \times 10^9/\text{L}$ in neonates, and above $1.0 \times 10^9/\text{L}$ in adults.

What absolute threshold defines monocytopenia, and what conditions or therapies cause it?

Absolute count $<0.2 \times 10^9/\text{L}$; observed with aplastic anemia, chemotherapy, steroid therapy, hemodialysis, sepsis, and Epstein-Barr virus (EBV) infections.

When is it appropriate to count 50 WBCs or 200 WBCs instead of the routine 100 cells on a differential count?

Count $50$ cells if total WBC count is $<1.0 \times 10^9/\text{L}$. Count $200$ cells if there are $>10\%$ eosinophils, $>2\%$ basophils, $>11\%$ monocytes, or more lymphocytes than neutrophils (except in children).

What is the difference between Schilling's classification and Arneth's classification of neutrophils?

Schilling's classifies neutrophils according to their granulations, while Arneth's classifies them according to age based on the number of nuclear lobes.

How is the Cross-Sectional (Crenellation) counting method performed on a blood smear?

WBCs are counted in consecutive fields as the blood film is moved from side to side.

How is the Longitudinal counting method performed on a peripheral blood smear?

WBCs are counted in consecutive fields beginning from the tail toward the head of the smear.

What specific slide scanning pattern used in WBC differential counts is depicted here?

Battlement method

What is the formula used to calculate the relative count percentage of a specific WBC type?

$$\% \text{ Relative Count} = \left(\frac{\text{number of specific cell type}}{100}\right) \times 100$$

What is the mathematical equation to calculate the absolute count of a WBC type?

$$\text{Absolute count} = \text{relative count} \times \text{total WBC count}$$

What are the normal adult reference ranges for peripheral blood percentage and absolute count of segmented neutrophils and band neutrophils?

Segmented neutrophils: $50\text{--}70\%$ (absolute: $1.7\text{--}7.5 \times 10^9/\text{L}$); Band neutrophils: $0\text{--}5\%$.

What are the adult reference ranges for the relative and absolute counts of lymphocytes, monocytes, eosinophils, and basophils?

Lymphocytes: $18\text{--}42\%$ ($1.0\text{--}3.2 \times 10^9/\text{L}$); Monocytes: $2\text{--}11\%$ ($1.3 \times 10^9/\text{L}$); Eosinophils: $1\text{--}3\%$ (up to $0.4 \times 10^9/\text{L}$ or $0.3 \times 10^9/\text{L}$); Basophils: $0\text{--}2\%$ (up to $0.2 \times 10^9/\text{L}$).