Unit Converter
Lymphocytes (LYMPH)
(Differential White Cell Percentage - Key Immune Pattern in Viral Illness, Autoimmunity & Hematologic Disorders)
Synonyms
- Lymphocyte percentage
- Lymphocyte fraction
- Lymph%
- Lymphocyte proportion
- Relative lymphocyte count
- Differential lymphocyte percentage
Units of Measurement
- %
- Proportion of 1.0
- Fraction
Unit Conversions
Percentage → Fraction
\text{Fraction} = \frac{\text{%}}{100}
Fraction → Percentage
\text{%} = \text{Fraction} \times 100
Example:
30% = 0.30 fraction
0.15 fraction = 15%
Description
Lymphocyte percentage (LYMPH%) is the relative proportion of lymphocytes among all white blood cells in the differential count.
It provides:
- Insight into immune balance
- Clues to infection types
- Key information when absolute lymphocyte count (ALC) is interpreted alongside WBC count
Lymphocytes include:
- T cells (CD4, CD8)
- B cells
- NK cells
Physiological Role
Lymphocytes are central to:
- Adaptive immunity
- Antibody production
- Viral clearance
- Tumor surveillance
- Immune memory
LYMPH% helps identify physiological vs pathological shifts in immune response.
Clinical Significance
HIGH LYMPH%
(Percent is high even if absolute count may be normal)
1. Viral Infections - Most Common
- EBV (infectious mononucleosis)
- CMV
- Viral hepatitis
- Influenza
- Adenovirus
- Early HIV
- COVID-19 recovery phase
2. Chronic Infections
- Tuberculosis
- Pertussis
3. Autoimmune Disorders
- Hashimoto thyroiditis
- Graves disease
- Rheumatoid arthritis
4. Lymphoproliferative Disorders
- Chronic lymphocytic leukemia (CLL)
- Often very high LYMPH% (60–90%)
- Often very high LYMPH% (60–90%)
- Lymphomas
5. Stress Recovery / Post-infection rebound
6. Hyperthyroidism
LOW LYMPH%
1. Bacterial Infections
Neutrophilia reduces LYMPH%.
2. Acute Stress Response
- Trauma
- Surgery
- Myocardial infarction
3. Corticosteroid Therapy
Redistribution → low LYMPH%.
4. Immunosuppression
- Chemotherapy
- Radiotherapy
5. Sepsis
Marked lymphopenia is a poor prognostic marker.
6. Autoimmune Diseases
- SLE (commonly low LYMPH%)
7. Protein-energy malnutrition
8. COVID-19
Relative lymphopenia is characteristic.
Reference Intervals
(Tietz 8E + WHO + Mayo + ARUP)
Adults
- 20 – 40%
(= 0.20 – 0.40 fraction)
Children
Children normally have much higher LYMPH% due to thymic activity.
| Age | Normal Range |
| Newborn | 20 – 40% |
| 6 months – 2 years | 40 – 70% |
| 2 – 6 years | 35 – 60% |
| >6 years | 25 – 45% |
Patterns to Note
- High LYMPH% + normal ALC = relative lymphocytosis
- High LYMPH% + high ALC = viral infection / CLL
- Low LYMPH% + low ALC = immunodeficiency / sepsis
Diagnostic Uses
1. Infection Patterns
- Viral illness → high LYMPH%
- Bacterial illness → low LYMPH%
2. Screening for Immunodeficiency
Low LYMPH% suggests:
- HIV
- Primary immunodeficiencies
- SCID (very low)
3. Hematologic Malignancies
High LYMPH% with atypical cells → CLL/lymphoma.
4. Autoimmune Disorders
Both high and low LYMPH% seen depending on disease/stage.
5. COVID-19
Low LYMPH% correlates with severity.
6. Treatment Monitoring
Used with ALC in patients receiving:
- Chemotherapy
- Immunosuppressants
- Steroids
Analytical Notes
- Automated analyzers calculate LYMPH% as part of CBC with differential
- Confirm abnormalities with peripheral smear
- LYMPH% must always be interpreted with ALC + total WBC
- Dehydration or hemoconcentration can skew percentages
Clinical Pearls
- Percentage alone can be misleading - always pair with absolute count.
- In CLL, LYMPH% often >60% even when WBC is massively elevated.
- In severe bacterial infections: high neutrophils + very low LYMPH%.
- Children normally have high LYMPH% - physiologic, not disease.
- Steroids cause LYMPH% to fall within hours via redistribution.
Interesting Fact
During early childhood, lymphocytes outnumber neutrophils - a physiologic phenomenon known as “lymphocyte predominance phase”, which reverses (“neutrophil predominance”) by around age 5.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Hematology
- WHO Hematology Standards
- Mayo Clinic Laboratories - Differential Count
- ARUP Consult - CBC Interpretation
- MedlinePlus / NIH - Lymphocyte Count