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Blast Cells, Number Fraction, Fetal Whole Blood

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

Measures the proportion of blast cells, or immature blood-forming cells, in a fetal whole-blood sample.

Quick summary

["An increased blast-cell proportion may indicate abnormal blood-cell production and requires clinical interpretation."]

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

Key facts at a glance

LOINC
74460-7
Short code
Blasts NFr Bld Fetus
Synonyms
Blasts NFr Bld Fetus
Category
liver
Sample
whole-blood
Container
Lavender-top (EDTA)
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
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?

This test measures the fraction or proportion of blast cells in fetal whole blood. Blast cells are immature cells produced in the bone marrow that normally represent only a small part of circulating blood.

Why might I need this test?

Fetal blood blast-cell testing may be performed when clinicians are evaluating possible blood-cell production problems around birth. It is usually interpreted with a complete blood count, differential count, and other hematologic tests.

How is the test performed?

A laboratory counts the blast cells in a fetal whole-blood specimen and reports their proportion relative to the cells examined. The specimen may be collected from the umbilical cord at delivery or obtained by another clinician-directed method.

How do I prepare for the test?

No specific fasting or medication instructions usually apply because this is generally a clinician-collected fetal or cord-blood specimen. Follow the instructions provided by the obstetric or pediatric team responsible for collection.

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

Fetal Blood Blast Cell Fraction

Frequently asked questions

What are blast cells?
Blast cells are immature blood-forming cells that normally develop in the bone marrow. Only a small proportion is normally expected to circulate in blood.
How is fetal blood usually collected?
It is often collected from the umbilical cord at delivery. The exact collection method depends on the clinical situation and the instructions from the care team.
Does an elevated blast-cell result mean my baby has leukemia?
No. An elevated result can have several causes and does not independently establish leukemia. A healthcare professional will interpret it alongside the complete blood count and other relevant 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