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HLA-DR–Expressing Blast Cells, Number Fraction, Whole Blood — Flow Cytometry

Published: August 9, 2026Updated: August 16, 2026

A flow cytometry test that measures the proportion of blast cells expressing HLA-DR in whole blood, often as part of leukemia evaluation.

Quick summary

["This test helps characterize blood cells when abnormal blasts are present, but results must be interpreted with other laboratory findings."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
107056-4
Short code
Blasts.HLA-DR+ NFr Bld FC
Synonyms
Blasts.HLA-DR+ NFr Bld FC
Category
liver
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
10
Ref high
40
Critical range
0.1 N/A – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
flow-cytometry
CPT
84484
SNOMED
302774002
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What is this test?

Blasts are immature blood cells that normally develop into healthy white blood cells. This test uses flow cytometry to identify blast cells that carry the HLA-DR marker and reports their fraction in a whole-blood sample.

Why might I need this test?

This test is usually ordered when a blood count, blood smear, or other findings suggest an abnormal number of immature cells. It can help characterize blasts as part of the evaluation or monitoring of acute leukemia and other blood disorders.

How is the test performed?

A blood sample is stained with fluorescent antibodies and analyzed by flow cytometry. The laboratory identifies cells with blast characteristics and determines how many express HLA-DR.

How do I prepare for the test?

No special preparation is usually required beyond standard blood-draw instructions. If you are receiving chemotherapy, steroids, or another treatment, ask the ordering clinician whether testing should be timed around it; do not stop medication on your own.

Reference range

Adult: 10-40 U/LN/A

Specimen: whole-blood

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

HLA-DR–Expressing Blast Cells

Frequently asked questions

Does a positive HLA-DR result mean that I have leukemia?
No. HLA-DR is a marker found on many normal immune cells, and a positive result does not establish a diagnosis of leukemia. The percentage and characteristics of the blast cells must be interpreted with the rest of the laboratory evaluation.
Why is HLA-DR checked on blast cells?
HLA-DR helps laboratory specialists characterize immature blood cells. When used with other markers, it can help distinguish different types of acute leukemia and support appropriate follow-up testing.
Can this test be used to monitor treatment?
It may be used alongside blood counts, bone marrow testing, and other flow cytometry markers to follow certain blood cancers. Timing may matter because chemotherapy or steroids can change the number and characteristics of circulating cells.
  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 16, 2026. · Read our editorial policy