Understanding Your Medical Test: What It Is, How It Is Done, and How to Get Ready
This test measures the number of basophils (a type of white blood cell) in fluid collected from body cavities to help diagnose infections, inflammation, or other medical conditions.
{"Basophils are white blood cells that help fight infections and regulate immune responses","This test analyzes fluid from areas like the lungs, abdomen, or spine","Elevated basophils may indicate infection, inflammation, or certain diseases","The test helps doctors determine the cause of abnormal fluid buildup","Results are interpreted alongside other tests for accurate diagnosis"}
Key facts at a glance
- LOINC
- 28543-7
- Short code
- BASOWBC
- Synonyms
- Basophils NFr Fld
- Category
- chemistry
- Sample
- serum
- Container
- Sterile body fluid collection container (plain tube for cell counts); EDTA tube acceptable for cellular preservation; heparinized tubes for synovial fluid to prevent clotting
- Units
- N/A
- Ref low
- 1000
- Ref high
- 5000
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- Automated cell count with manual microscopic differential; flow cytometry and Wright-Giemsa stained smear review
- CPT
- 89051
- SNOMED
- 40698007
- Specimen volume
- 1-5 mL minimum depending on fluid type; 5-10 mL preferred for adequate cell count and differential analysis
- Stability
- Room temperature: 1-2 hours; refrigerated (2-8°C): up to 4 hours. Cell morphology degrades rapidly. Best results obtained when analyzed within 1 hour of collection.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 1–4 hours
- Order
- routine
What is this test? This test is a diagnostic procedure that gives your healthcare provider important information about your health. It helps identify diseases, monitor ongoing conditions, and guide treatment decisions so you and your care team can make informed choices together.
The Basophils/Leukocytes in Body Fluid test measures the number and percentage of basophils in fluid collected from body cavities. Basophils are a type of white blood cell (leukocyte) that play an important role in your immune system's response to allergens, infections, and inflammation. This test is performed on fluid from areas such as the pleural space (around the lungs), peritoneal cavity (abdomen), or cerebrospinal fluid (spine).
How is the test performed? A trained member of your care team performs the test in a clinic, hospital, or laboratory setting. The exact steps depend on the type of test, but most procedures are quick, cause only mild discomfort, and let you go home the same day.
A healthcare provider will collect a sample of fluid from the affected body area using a needle and syringe. This procedure is called paracentesis (abdomen), thoracentesis (chest), or lumbar puncture (spine), depending on the location. The collected fluid is then sent to a laboratory where specialists examine it under a microscope to count and identify the different types of white blood cells, including basophils.
Why might I need this test? Your doctor may recommend this test to find the cause of symptoms you are experiencing, screen for conditions before they cause problems, check how well a current treatment is working, or monitor a chronic condition over time.
Your doctor may order this test if you have abnormal fluid buildup in your body cavities that needs to be evaluated. Common reasons include unexplained pleural effusion (fluid around the lungs), ascites (fluid in the abdomen), or suspected infections in these areas. The test helps determine whether the fluid is caused by infection, cancer, inflammatory conditions, or other medical problems.
How should I prepare? Your care team will give you specific instructions before the test. In general, tell your provider about all medicines and supplements you take, ask whether you need to fast, wear comfortable clothing, and arrange a ride home if sedation may be used.
Preparation depends on which body area will be sampled. Your healthcare provider will give you specific instructions. You may need to fast before an abdominal fluid collection. For chest or spine procedures, you may need to wear a hospital gown and follow specific positioning instructions. Always inform your doctor about medications you are taking, as some may need to be adjusted before the procedure.
Reference range
Reference values vary by body fluid type. Pleural fluid: Basophils <1%, Leukocytes 1000-5000/μL. Peritoneal (ascitic) fluid: Basophils <1%, Leukocytes <500/μL. Synovial fluid: Basophils <1%, Leukocytes <200/μL. CSF: Basophils <1%, Leukocytes 0-5/μL. Consult fluid-specific reference ranges for clinical interpretation.N/A
No fasting required. Specimen collection site and technique must be documented. Aseptic technique is mandatory. Specimen should be delivered to laboratory promptly to prevent cell lysis and inaccurate counts.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Normal basophil counts in body fluid are typically very low or absent. Elevated basophil levels may indicate allergic reactions, parasitic infections, chronic inflammation, or certain blood disorders. In some cases, basophils may be present in fluid due to malignant conditions. The interpretation of results requires consideration of your overall clinical condition, symptoms, and other laboratory findings. Your healthcare provider will discuss what your specific results mean for your health situation.
Frequently asked questions
Is the fluid collection procedure painful?
How long does it take to get results?
Are there any risks associated with this test?
What do high basophil levels mean?
Will I need other tests along with this one?
Sources
- 1
- 2Mayo Clinic - AscitesSource
- 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