Understanding Your Laboratory Test: A Complete Patient Guide to Testing, Sample Collection, and Results
A laboratory test that counts basophil cells in the fluid from a joint to help diagnose joint inflammation or disease.
{"Basophils are a type of white blood cell that plays a role in inflammation and allergic reactions","This test examines joint (synovial) fluid to help diagnose arthritis, infections, or joint damage","The test is performed manually under a microscope by counting basophils in the fluid sample","Results help doctors determine the cause of joint pain, swelling, or stiffness","Normal basophil counts in synovial fluid are typically very low or absent"}
Key facts at a glance
- LOINC
- 68395-3
- Short code
- SYNBASO
- Synonyms
- Basophils # Snv Manual
- Category
- chemistry
- Sample
- fluid
- Container
- Sterile, anticoagulated collection tube (sodium heparin or EDTA) for cell counts; plain sterile tube for concurrent chemistries/microbiology
- Units
- N/A
- Ref low
- 0
- Ref high
- 0
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- manual-count
- CPT
- 89051
- SNOMED
- 44667007
- Specimen volume
- 1-5 mL of synovial fluid; minimum 0.5 mL required for manual cell count
- Stability
- Specimen should be processed within 1 hour of collection for accurate cell counts. If delayed, refrigerate at 2-8°C and process within 4 hours. Do not freeze.
- Hemolysis max
- 300
- TAT
- 1–4 hours
- Order
- routine
This test is a laboratory analysis performed on a sample of your blood, urine, or other body fluid to help your healthcare provider evaluate your overall health, screen for medical conditions, monitor an ongoing illness, or check how well a treatment is working.
The Synovial Fluid Basophil Count is a laboratory test that measures the number of basophils (a type of white blood cell) in the fluid collected from a joint. Synovial fluid is the thick, slippery liquid that cushions and lubricates the joints, allowing smooth movement. This test is performed manually by examining the fluid sample under a microscope and counting the basophils present.
A trained healthcare professional will collect the sample during a quick office or clinic visit. Most samples are drawn from a vein in your arm using a small needle, although some tests require a urine, saliva, or swab specimen, and you will receive detailed instructions if any preparation is needed at home beforehand.
A healthcare provider will use a needle to withdraw a small amount of synovial fluid from the affected joint, a procedure called joint aspiration or arthrocentesis. The area will be cleaned and numbed to minimize discomfort. The collected fluid is then sent to a laboratory where a technician performs the manual cell count.
Your doctor orders this test to gather important information about your body, such as confirming or ruling out a diagnosis, identifying risk factors before symptoms appear, tracking changes in an existing condition over time, and guiding decisions about the safest and most effective treatment plan for you.
This test is ordered when a patient experiences joint pain, swelling, redness, or stiffness. It helps doctors evaluate the cause of these symptoms by examining the cellular composition of the synovial fluid. The presence and number of basophils can indicate inflammatory conditions, allergic reactions within the joint, or other joint disorders.
Reference range
Basophils are normally absent or extremely rare in synovial fluid. Expected value: 0 cells/µL (rare or none); typically <1% of total leukocyte count.N/A
No fasting required. Inform patient of arthrocentesis procedure including potential discomfort, bleeding risk, and infection risk. Skin over the joint should be cleaned with antiseptic prior to aspiration. Discontinue anticoagulants if clinically feasible per physician guidance.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated basophil counts in synovial fluid may indicate inflammatory arthritis (such as rheumatoid arthritis), gout, pseudogout, joint infection (septic arthritis), or other inflammatory conditions. Basophils contain histamine and other inflammatory mediators, so their presence in increased numbers suggests an active inflammatory or allergic process within the joint. Normal or very low basophil counts are typically found in non-inflammatory conditions like osteoarthritis. This test, combined with other synovial fluid analyses (like white blood cell count, crystal analysis, and culture), helps doctors diagnose the specific cause of joint problems and guide appropriate treatment.
Frequently asked questions
Is the joint aspiration procedure painful?
How long does it take to get results?
Are there any risks associated with this test?
Do I need to prepare for the test?
What happens after the test?
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