Basophils
Basophils· also: Basophils
Clinical Overview
Basophils are the least common white blood cells, making up less than 1% of circulating leukocytes. They are involved in immediate allergic reactions and inflammation, releasing histamine, heparin, and other mediators. Basophilia is rare but is the hallmark of certain myeloproliferative disorders.
Why This Test Matters
Basophilia (elevated basophils) is rare and should always prompt consideration of chronic myeloid leukemia (CML), polycythemia vera, or essential thrombocythemia. A markedly elevated basophil count in CML precedes blast crisis. Basophils are also elevated in severe allergic reactions and hypothyroidism.
Reference RangesWHO/IFCC standards
| Age Group | Reference Range | Unit | Notes |
|---|---|---|---|
| Adults (18–64) | 0 – 0.1 | ×10³/µL | — |
Also reported in: %.
What Causes Abnormal Results?
High Basophils Causes
- Chronic myeloid leukemia (CML) — most important cause
- Polycythemia vera
- Essential thrombocythemia
- Severe allergic reactions
- Hypothyroidism
- Inflammatory bowel disease
Low Basophils Causes
- Corticosteroid therapy
- Acute allergic reactions (paradoxical drop due to degranulation)
- Hyperthyroidism
Signs & Symptoms to Watch For
How to Prepare for This Test
No preparation needed. Part of CBC differential.
Factors That Can Affect Results
- Steroids (lower basophil count)
- Sample age (basophils degrade quickly in stored samples)
Related Topics
Frequently Asked Questions
Why are high basophils associated with CML?
In chronic myeloid leukemia, the BCR-ABL fusion gene drives uncontrolled production of all myeloid cell lines, including basophils. Basophilia (basophils >1% or >100/µL) is one of the diagnostic features of CML. Rising basophil counts during treatment may signal disease progression toward accelerated phase or blast crisis. CML is confirmed by detecting the BCR-ABL translocation (Philadelphia chromosome).