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Blast Cell Count, Synovial Fluid — Manual Count

Published: August 9, 2026Updated: August 17, 2026

Counts blast cells in fluid removed from a joint to help evaluate whether a blood cancer or another serious condition may be affecting the joint.

Quick summary

["An elevated blast-cell count in joint fluid may suggest involvement by a leukemia or lymphoma."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
13522-8
Short code
Blasts NFr Fld Manual
Synonyms
Blasts NFr Fld Manual
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
manual-count
CPT
84484
SNOMED
302774002
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

This test examines synovial fluid, the lubricating liquid inside a joint, for blast cells. Blast cells are immature blood-forming cells that are not normally expected to be present in joint fluid.

Why might I need this test?

A clinician may order this test when a joint is swollen, painful, or filled with fluid and the cause is unclear. It can help evaluate concern for joint involvement by a blood cancer, particularly in people with a known or suspected leukemia or lymphoma.

How is the test performed?

Joint fluid is usually collected through a procedure called arthrocentesis. A laboratory professional then counts and reviews the cells manually under a microscope as part of the fluid analysis.

How do I prepare for the test?

No special preparation is usually required for the laboratory count itself. Follow your clinician's instructions for joint-fluid collection, and tell the healthcare team if you have a bleeding disorder, take blood thinners, or have a joint infection.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Synovial Fluid Blast Count

Frequently asked questions

Are blast cells normally found in joint fluid?
No. Blast cells are immature blood-forming cells and are not normally expected to be present in synovial fluid.
Does a positive result mean someone has leukemia?
Not by itself. Detected blast cells can raise concern for leukemia or lymphoma involving the joint, but other laboratory and clinical findings are needed to confirm the cause.
Is this test the same as a routine joint-fluid cell count?
It is a specific part of synovial-fluid analysis in which laboratory professionals look for blast cells. The report may also include the total cell count, differential cell count, crystals, glucose, protein, and other findings.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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 17, 2026. · Read our editorial policy