Basophils Blood Test (Basophil Count)
This test checks for the presence of basophils (a type of white blood cell) in fluid collected from around the lungs.
{"Basophils are white blood cells that help fight infection and regulate immune responses","This test examines pleural fluid (fluid around the lungs) using a microscope","Elevated basophils may indicate infection, inflammation, or other conditions","Results help doctors determine the cause of fluid buildup in the chest","The test is part of a complete fluid analysis"}
Key facts at a glance
- LOINC
- 44043-8
- Short code
- BASO-PL
- Synonyms
- Basophils Plr Ql Micro
- Category
- chemistry
- Sample
- fluid
- Container
- Sterile pleural fluid collection tube (EDTA or heparin anticoagulant tube) for cell count and differential; sterile container without anticoagulant for biochemistry
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- microscopy-light
- CPT
- 89051
- SNOMED
- 104283003
- Specimen volume
- Minimum 5-10 mL of pleural fluid; preferably 20-50 mL for comprehensive analysis
- Stability
- Room temperature: 1-2 hours for optimal cell morphology; refrigerated (2-8°C): up to 4 hours; for delayed analysis, prepare cytocentrifuge slides within 1 hour of collection
- Hemolysis max
- 300
- TAT
- 1–4 hours
- Order
- routine
This test measures the number of basophils in your blood. Basophils are a type of white blood cell, and this measurement is usually performed as part of a complete blood count (CBC) with differential. It helps your doctor evaluate allergic reactions, infections, inflammation, and certain blood disorders, and it can be used to monitor an existing condition or the effect of treatment.
The Basophils [Presence] in Pleural Fluid test is a laboratory examination that looks for basophils in a sample of pleural fluid. Pleural fluid is the thin liquid that naturally exists in the space between your lungs and chest wall. When excess fluid accumulates in this area (a condition called pleural effusion), doctors may need to drain and analyze it to find out what is causing the buildup.
A healthcare professional will wrap a band around your upper arm, clean the skin, and draw a small sample of blood from a vein, usually in your arm or hand. The needle may cause a brief sting, but the procedure typically takes only a few minutes. The sample is then sent to a laboratory, where special equipment counts the different types of white blood cells, including basophils, and your doctor will review the results with you.
A healthcare provider will first collect a sample of pleural fluid through a procedure called thoracentesis, where a thin needle is inserted into the chest cavity to remove fluid. This sample is then examined under a microscope in a laboratory to detect and count the presence of basophils.
Basophils are one of the main types of white blood cells and are part of your immune system. They help defend your body against infections and release histamine and other chemicals during allergic reactions, which can cause symptoms such as swelling, itching, and runny nose. Basophils normally make up a very small percentage of your total white blood cells, so changes in their number can provide important clues about your health.
Basophils are a type of white blood cell that play an important role in your immune system. They help protect your body by responding to allergens (substances that cause allergic reactions) and fighting certain infections. While basophils normally make up only a small percentage of white blood cells, their presence in abnormal locations can provide important diagnostic information.
Reference range
Basophils are normally absent or rare in pleural fluid. Presence of basophils may suggest underlying allergic, parasitic, or neoplastic processes.N/A
No special patient preparation is required. Thoracentesis is performed by qualified healthcare personnel under sterile conditions with appropriate local anesthesia.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The presence of basophils in pleural fluid can help doctors identify the cause of pleural effusion. Elevated basophils may be associated with various conditions including bacterial or viral infections, inflammatory diseases, certain cancers (such as leukemia or lymphoma), or allergic reactions. However, basophils are not always present in these conditions, and the results must be interpreted alongside other test findings, including the overall appearance of the fluid, cell counts, and chemical composition.
Your doctor will consider these test results along with your symptoms, imaging studies, and other laboratory tests to make an accurate diagnosis and determine the most appropriate treatment plan.
Frequently asked questions
Is this test painful?
How long does it take to get results?
Do I need to prepare for this test?
What happens if basophils are found in my pleural fluid?
Sources
- 1
- 2MedlinePlus - BasophilsSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy