Blood Test Overview: What to Expect and Why It Matters
This test counts the number of basophils, a type of white blood cell, in a sample of body fluid to help diagnose infections, inflammation, or other medical conditions.
{"Basophils are white blood cells that play a role in allergic reactions and immune responses","This test is performed on body fluid samples such as pleural, peritoneal, or synovial fluid","Abnormal results may indicate infection, inflammation, allergic reactions, or certain blood disorders","The test is done using manual microscopic examination","Results are interpreted together with other tests and clinical symptoms"}
Key facts at a glance
- LOINC
- 40571-2
- Short code
- BASOBF
- Synonyms
- Basophils # Fld Manual
- Category
- chemistry
- Sample
- serum
- Container
- Sterile, leak-proof container without anticoagulant preferred; EDTA tube acceptable for some fluid types; sterile plain tube for microbiology correlation
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- manual-count
- CPT
- 89051
- SNOMED
- 395065009
- Specimen volume
- 1-3 mL minimum; larger volumes preferred for adequate cellularity assessment
- Stability
- Refrigerate at 2-8°C; analyze within 1-2 hours of collection for optimal cell morphology; maximum stability 4 hours refrigerated
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 1–4 hours
- Order
- routine
What is this test, and what does it measure in my body?
The basophil count in body fluid is a laboratory test that measures the number of basophils present in a sample of body fluid. Basophils are a type of white blood cell (leukocyte) that are part of the immune system. They play an important role in allergic reactions, inflammation, and defending the body against parasites. This test is performed manually under a microscope by a trained laboratory technician who identifies and counts the basophils in the fluid sample.
Why is this test performed, and what can my doctor learn from it?
This test may be ordered when a patient has excess fluid accumulation in a body cavity (such as pleural effusion in the chest, ascites in the abdomen, or synovial fluid in joints). The test helps doctors determine the cause of the fluid accumulation—whether it's due to infection, inflammation, cancer, or other conditions. It provides valuable information about the immune response occurring in the affected area.
How is this test done, and what should I expect during the procedure?
A healthcare provider will collect a sample of body fluid using a needle and syringe (a procedure called paracentesis, thoracentesis, or arthrocentesis depending on the fluid location). The sample is then sent to a laboratory where a technician examines it under a microscope. The basophils are identified by their characteristic appearance (cells with dark-staining granules) and counted. Results are typically reported as a number or percentage of total cells present.
What do the results of this test mean for my overall health?
Results should be interpreted by your healthcare provider in the context of your overall health, symptoms, and other test results. The presence and number of basophils in body fluid can help differentiate between different types of conditions. Your doctor will explain what your specific results mean for your health situation.
Reference range
Reference values for basophils in body fluid are not well established and interpretation depends on clinical context and fluid type (e.g., pleural, peritoneal, synovial, CSF). Generally, basophils are rarely present in body fluids; presence is reported qualitatively or as a percentage of total leukocytes.N/A
No special patient preparation required. Specimen collection should follow aseptic technique appropriate for the body fluid sampling site (e.g., thoracentesis, paracentesis, arthrocentesis, lumbar puncture).
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated basophils in body fluid may indicate an allergic or inflammatory reaction, parasitic infection, or certain blood disorders. In some cases, it may be associated with autoimmune conditions or malignancies. Low basophils in body fluid are less common but may occur in severe infections or immunodeficiencies. The interpretation of basophil counts in body fluid must be done alongside analysis of other cell types (like neutrophils, lymphocytes, and eosinophils) and the overall fluid characteristics to determine the underlying cause.
Frequently asked questions
Is this test painful?
How long does it take to get results?
Do I need to fast before this test?
What are the risks of having fluid collected?
Can basophils in blood also be tested?
Sources
- 1
- 2
- 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