Lymphocyte

Lymphocyte Result

Reference range: 0.80-4.00 ×10⁹/L

 

What is Lymphopenia?

Lymphopenia refers to a reduced lymphocyte count, typically < 1.0 ×10⁹/L in adults. It may reflect immunosuppression or an underlying disease process.

Common Causes

  • Acute infections (especially viral)
  • Sepsis or critical illness
  • HIV infection
  • Steroid therapy or other immunosuppressants
  • Haematological malignancies (e.g. lymphoma)
  • Autoimmune disorders (e.g. SLE)
  • Post-chemotherapy or radiotherapy

Stepwise Clinical Approach

Step 1: Confirm and Repeat

Verify lymphocyte count is truly low. If mild and asymptomatic, repeat FBC in 1-2 weeks to exclude transient lymphopenia (e.g. post-viral).

When repeating, also request:

  • HIV test: to exclude undiagnosed HIV, a common cause of persistent lymphopenia
  • Immunoglobulin levels: to assess for secondary immunodeficiency
  • ANA and ENA panel: to screen for underlying autoimmune conditions such as SLE
  • CXR: to check for mediastinal masses (e.g. lymphoma) or TB
  • Flow cytometry: if lymphopenia persists or if abnormal cells are detected on blood film

These tests help differentiate between transient causes and serious underlying conditions.

Step 2: Identify Red Flags

  • Persistent lymphocytes < 0.5 ×10⁹/L
  • Recurrent infections or failure to recover from illness
  • Systemic symptoms (e.g. unexplained weight loss or night sweats)
  • Unexplained lymphadenopathy or hepatosplenomegaly

If present → consider urgent referral or specialist review (e.g. immunology, haematology).

Step 3: Review Medications and History

  • Recent steroid or cytotoxic drug use?
  • History of chemotherapy, HIV, or autoimmune disease?
  • Recent infections or hospitalisation?

Many cases are medication-related or transient post-viral.

Step 4: Interpret Repeat Results

  • If recovered: likely transient and no further action needed
  • If persistent: escalate for further investigation

Step 5: Monitor or Refer

  • If mild (0.8–1.0 ×10⁹/L) and asymptomatic: monitor every 3–6 months
  • If moderate/severe or symptomatic: refer to haematology or immunology
 

What is Lymphocytosis?

Lymphocytosis refers to an increased number of lymphocytes in the blood, usually > 5 ×10⁹/L. It may be reactive (benign) or malignant (e.g. leukaemia).

Common Causes

  • Viral infections (e.g. glandular fever, hepatitis)
  • Chronic lymphocytic leukaemia (CLL)
  • Smoking
  • Post-splenectomy states
  • Autoimmune conditions (e.g. rheumatoid arthritis)

Stepwise Clinical Approach

Step 1: Confirm the Count

Review if lymphocyte count is truly elevated (> 5 ×10⁹/L). Repeat FBC if unclear or borderline.

Step 2: Screen for Red Flags

Ask about:

  • Unexplained weight loss
  • Fevers not due to infection
  • Night sweats
  • Lymphadenopathy or splenomegaly

If present → refer urgently to haematology (possible malignancy).

Step 3: Repeat FBC and Request Additional Tests

If the patient is well and no red flags are present, repeat FBC after 6 weeks to assess persistence.

When repeating, also request:

  • Blood film: to assess for abnormal lymphocyte morphology (e.g. smear cells in CLL)
  • CRP/ESR: to screen for underlying inflammation or infection
  • Immunoglobulins: to detect hypogammaglobulinaemia, which can be associated with CLL
  • LDH: as a marker of cell turnover (can be raised in lymphoproliferative disorders)

These additional tests help distinguish between benign reactive causes and early signs of lymphoproliferative disease.

Step 4: Interpretation of Repeat FBC

  • < 10 ×10⁹/L: Consider reactive cause → monitor 6-monthly if stable.
  • Persistent > 10 ×10⁹/L: Consider haematology referral.

Step 5: Don’t Miss These!

  • CLL may present gradually — even in asymptomatic older adults
  • Always review blood film carefully, especially if smear cells or atypical lymphocytes present
  • Consider imaging (e.g. ultrasound) if significant lymphadenopathy detected clinically
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