Create a study guide comparing normal vs. abnormal DLC patterns

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DLC (Differential Leukocyte Count) Study Guide

Normal vs. Abnormal Patterns

1. What Is the DLC?

The DLC quantifies the relative (%) and absolute (cells/µL) concentration of each leukocyte type in peripheral blood. It is part of the automated CBC and is reviewed by a skilled technologist when abnormal flags appear.

Key principle: Always use the absolute count (WBC total × cell %), not just the percentage, to determine a true abnormality. A raised % of one cell type can simply reflect a reduction in another.

Normal total WBC in adults: 4,000-7,000 cells/µL (broader reference: ~4,500-11,000/µL).

2. Normal DLC Reference Ranges (Adults)

Cell Type	% of WBC	Absolute Count (×10³/µL)	Notes
Neutrophils (segs + bands)	50-70%	1.8-7.0	Bands normally <5%
Lymphocytes	20-40%	1.0-4.8	Dominant in children <4 yrs
Monocytes	2-10%	0.2-1.0	Largest circulating WBC
Eosinophils	1-4%	0.04-0.4	Elevated in allergies/parasites
Basophils	0-1%	0.01-0.1	Rarest; carrier of histamine

Reference ranges may vary slightly by laboratory, age, and sex.

3. NEUTROPHILS

Normal Morphology

Segmented (3-5 nuclear lobes), pale pink cytoplasm with fine pink-purple granules
Bands: horseshoe/U-shaped nucleus, normally <5%

Neutrophilia (Neutrophilic Leukocytosis)

Definition: Absolute neutrophils >7.0 ×10³/µL in adults

Mechanisms:

Demargination/pseudoneutrophilia - epinephrine, exercise, stress release cells from marginal granulocyte pool (MGP) to circulating pool; no increase in total granulocyte pool
Increased marrow output - cortisol/steroids, severe infections
Decreased egress from blood - corticosteroids block migration to tissues

Causes (Box 34.1 - Henry's):

Category	Examples
Infections	Bacterial (most common), fungal, some viral
Inflammation	Trauma, surgery, burns, MI
Drugs	Corticosteroids, G-CSF, lithium
Physiologic	Exercise, stress, pregnancy, neonatal period
Neoplastic	CML, myeloproliferative disorders
Metabolic	Uremia, diabetic ketoacidosis, gout
Other	Asplenia, hemorrhage, hemolysis

Exceptions to neutrophilia in bacterial infection: Tuberculosis, brucellosis, pertussis (lymphocyte-dominant), Listeria infections (monocyte-dominant).

Left Shift: Increased immature neutrophils (bands, metamyelocytes, myelocytes) released from marrow. Reactive left shift rarely includes promyelocytes or blasts. Accompanies severe infections.

Toxic Changes (seen in severe infection/inflammation):

Change	Description
Toxic granulation	Dark azurophilic (primary) granules; severe infections and toxic conditions
Döhle bodies	Pale-blue oval cytoplasmic inclusions (ribosome remnants); infections and toxic states
Cytoplasmic vacuoles	Indicate active phagocytosis

Neutropenia

Definition: Absolute neutrophils <1.8 ×10³/µL (adults); higher threshold in young children

Severity grading:

Mild: 1.0-1.8 ×10³/µL
Moderate: 0.5-1.0 ×10³/µL
Severe (agranulocytosis): <0.5 ×10³/µL - high infection risk

Key Causes:

Category	Examples
Drugs (most common)	Chemotherapy, chloramphenicol, sulfonamides, phenothiazines, antithyroids, anticonvulsants
Radiation	Dose-dependent marrow damage
Toxins	Alcohol, benzene
Immune-mediated	SLE, RA/Felty syndrome, AIDS
Congenital	Kostmann syndrome, cyclic neutropenia (21-day cycling, ELA2 mutations), Chédiak-Higashi
Hematologic	Megaloblastic anemia, myelodysplasia, aplastic anemia, marrow infiltration
Infectious	Overwhelming bacterial infection; measles, rubella (viral-mediated suppression)
Other	Starvation, hypersplenism

Note: Toxic granulation, left shift, and Döhle bodies are seen with infection-related neutropenia but NOT in neutropenia of pregnancy-induced hypertension (PIH) - a useful distinguishing feature.

Morphological Anomalies of Neutrophils

Anomaly	Description	Significance
Pelger-Huët	Bilobed/"pince-nez" nucleus	Inherited (benign) or acquired in MDS
Hypersegmentation	≥5 lobes; ≥5% have ≥5 lobes	Megaloblastic anemia (B12/folate deficiency)
Alder-Reilly	Prominent azurophilic granulation	Not infection-related; mucopolysaccharidoses
May-Hegglin	Döhle-like inclusions + giant platelets	Rare autosomal-dominant anomaly
Chédiak-Higashi	Giant fused granules (lysosomes) in all leukocytes	Autosomal-recessive; recurrent pyogenic infections, partial albinism

4. LYMPHOCYTES

Lymphocytosis

Definition: Absolute lymphocytes >4.8 ×10³/µL (adults); physiologically normal in children

Causes:

Category	Examples
Acute viral infections	EBV (mononucleosis), CMV, hepatitis, rubella, pertussis
Chronic infections	TB, brucellosis, toxoplasmosis
Autoimmune	Early RA, other autoimmune disorders
Neoplastic	CLL (chronic lymphocytic leukemia), ALL, lymphomas

Reactive lymphocytes (atypical lymphocytes): Larger cells with abundant blue-gray cytoplasm and eccentric kidney-shaped nucleus. Classically seen in EBV infectious mononucleosis. Represent T-cell activation in response to viral antigens.

Lymphopenia (Lymphocytopenia)

Definition: Absolute lymphocytes <1.0 ×10³/µL

Causes:

Category	Examples
Immunodeficiency	HIV/AIDS, DiGeorge syndrome, SCID
Adrenocortical excess	Cushing's syndrome, high-dose corticosteroids
Cytotoxic therapy	Chemotherapy, radiation (lymphocytes are most radiosensitive)
Advanced malignancy	Lymphomas, carcinomas
Other	Impaired intestinal lymphatic drainage, anorexia nervosa

5. MONOCYTES

Monocytosis

Definition: Absolute monocytes >1.0 ×10³/µL

Causes:

Category	Examples
Infections	Tuberculosis, brucellosis, subacute bacterial endocarditis, Listeria, protozoal
Hematologic	Acute monocytic leukemia (AML-M5), AML-M4, MDS
Inflammatory	SLE, IBD, sarcoidosis
Recovery phase	Post-chemotherapy/radiation (monocytes recover before neutrophils)
GI disorders	Sprue, ulcerative colitis
Drug reactions	Various

Special note: A monocytic response is the predominant WBC change in Listeria monocytogenes infection (especially in neonates).

Monocytopenia

Causes: Onset of steroid therapy; hairy cell leukemia (characteristic finding). Isolated monocytopenia is not usually considered pathologic.

6. EOSINOPHILS

Eosinophilia

Definition: Absolute eosinophils >0.4 ×10³/µL (>4% on differential)

Grading:

Mild: 0.4-1.5 ×10³/µL
Moderate: 1.5-5.0 ×10³/µL
Severe/Hypereosinophilia: >5.0 ×10³/µL

Causes:

Category	Examples
Allergic	Asthma, hay fever, urticaria, atopic dermatitis, angioedema
Parasitic	Tissue-invasive helminths (Ascaris, hookworm, Toxocara, Strongyloides)
Neoplastic	CML, eosinophilic leukemia, Hodgkin lymphoma, solid tumor metastases
Cutaneous	Eczema, psoriasis, pemphigus
Pulmonary	Löffler syndrome, eosinophilic pneumonia
Drug reactions	NSAIDs, antibiotics
Other	Addison disease, post-irradiation, Lyme disease, rheumatic fever

In synovial fluid: Eosinophilia >2% of leukocyte count reported in Lyme disease, RA, rheumatic fever, metastatic carcinoma, allergic reactions to contrast dye.

Eosinopenia

Definition: Absolute eosinophils <0.04 ×10³/µL (often difficult to detect due to normally low counts)

Causes: Acute physical stress, acute inflammatory states, Cushing's syndrome, corticosteroid therapy.

7. BASOPHILS

Basophilia

Definition: Absolute basophils >0.1 ×10³/µL

Causes:

Category	Examples
Hematologic (most specific)	CML (very characteristic), polycythemia vera, myeloid metaplasia
Inflammatory/allergic	Hypersensitivity reactions, chronic sinusitis
Endocrine	Hypothyroidism
Other	Chronic hemolytic anemia, splenectomy, ionizing radiation

Important clinical pearl: Persistent basophilia in combination with neutrophilia and eosinophilia strongly suggests CML (check for BCR-ABL fusion gene / Philadelphia chromosome).

Basopenia

Definition: Absolute basophils <0.01 ×10³/µL (difficult to detect given normally very low count)

Causes: Sustained glucocorticoid treatment, acute infection or stress, hyperthyroidism.

8. Quick Pattern Recognition Table

Pattern	First Diagnosis to Suspect
Neutrophilia + left shift + toxic changes	Bacterial infection / sepsis
Neutrophilia alone (no toxic changes)	Physiologic stress, corticosteroids
Neutropenia + no toxic changes	Drug effect, PIH, immune-mediated
Lymphocytosis + atypical lymphocytes	EBV infectious mononucleosis
Lymphocytosis + mature small lymphocytes	CLL
Eosinophilia (mild-moderate)	Allergy, atopic disease
Eosinophilia (marked)	Tissue-invasive parasites
Basophilia	CML (until proven otherwise)
Monocytosis	TB, chronic infection, AML-M5
Lymphopenia	HIV/AIDS, corticosteroids, radiation
Pancytopenia	Aplastic anemia, marrow infiltration, megaloblastic anemia
Neutrophilia + basophilia + eosinophilia	CML (leukemoid reaction if no BCR-ABL)

9. DLC Patterns in Specific Diseases

Disease	Classic DLC Pattern
Bacterial sepsis	Neutrophilia, left shift, toxic granulation, Döhle bodies
Viral infection (EBV)	Lymphocytosis with atypical (reactive) lymphocytes
CML	Neutrophilia, basophilia, eosinophilia; all myeloid stages present; BCR-ABL+
CLL	Lymphocytosis of mature-looking small lymphocytes
Pertussis	Lymphocytosis (not neutrophilia, unusually for bacterial cause)
Tuberculosis	Lymphocytosis or monocytosis; neutropenia possible
Parasitic infection	Eosinophilia (tissue-invasive species especially)
Allergic reaction	Eosinophilia ± basophilia
HIV/AIDS	Lymphopenia (especially CD4+ T cells), neutropenia
Felty syndrome	Neutropenia + RA + splenomegaly
B12/folate deficiency	Hypersegmented neutrophils, pancytopenia
Addison's disease	Eosinophilia, lymphocytosis, neutropenia
Cushing's syndrome	Neutrophilia, lymphopenia, eosinopenia

10. Key Formulas

Absolute count = Total WBC × (% of cell type / 100)
Leukocyte count correction for nRBCs = WBC × 100 / (100 + number of nRBCs per 100 WBCs)

Sources

Henry's Clinical Diagnosis and Management by Laboratory Methods (23rd ed.), Chapters 12, 14
Textbook of Family Medicine (9th ed.), Chapter 14
Goldman-Cecil Medicine (International Edition), Chapter 143
Quick Compendium of Clinical Pathology (5th ed.)
Tietz Textbook of Laboratory Medicine (7th ed.)

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Slide	Content
1	Title slide (dark navy background)
2	What Is the DLC? + Normal Reference Ranges table
3	Neutrophilia - morphology, mechanisms, causes
4	Left Shift, Toxic Changes + Morphological Anomalies
5	Neutropenia - severity grading + causes
6	Lymphocytosis vs. Lymphopenia (side by side)
7	Monocytes vs. Eosinophils (side by side)
8	Basophilia & Basopenia
9	Quick Pattern Recognition table (green color-coded)
10	DLC in Specific Diseases (amber color-coded)
11	Key Formulas + Sources
12	Closing slide

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DLC Study Guide v2
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(384 KB, 12 slides)

Here's what changed in the new style:

	Old Style	New Style
Background	Off-white/grey	Clean white throughout
Headers	Dark navy bar	Deep clinical green bar
Accent	Blue, red, amber, yellow mix	Green + teal (with red only for danger labels)
Layout	Dense, many tables per slide	More whitespace, cards for mechanism slides
Title slide	Full-width colour block	Split panel (green left, white right)
Section dividers	None	Large watermark number + title
Fonts	Mixed weights	Calibri throughout, lighter body weight
Tables	Alternating blue rows	Alternating soft green rows
Callout notes	Blue left-border	Teal left-border with teal tint background

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DLC Study Guide v3
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(422 KB · 12 slides)

Here's what was upgraded visually:

Element	What changed
Title slide	Large "DLC" type with gold rule, "WBC" watermark, left panel split — cinematic feel
Header bar	Deep forest green + warm gold underline stripe on every content slide
Cards	Subtle drop shadows on all cards and tables for depth
Severity badges	Styled with drop shadow + gold bottom edge for polish
Callout notes	Gold left-icon block + pale gold background instead of plain teal
Tables	Alternating white / soft mint rows with thin grey borders, shadow behind each table
Closing slide	Gold top + bottom border, large "Thank You" centred
Color discipline	Forest green dominant · gold as the single accent · rose only for danger · sky blue for secondary cells
Typography	Controlled hierarchy: 21pt headers · 12pt body · 9–10pt table cells — nothing competing

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