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Red Blood Cell CD59 Deficient Number Fraction, Blood

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

This blood test measures the fraction of red blood cells that lack normal CD59, a protein that protects cells from complement-mediated damage. It is commonly used in the evaluation of suspected paroxysmal nocturnal hemoglobinuria (PNH).

Quick summary

["Detecting CD59-deficient red blood cells can support the evaluation of PNH, but results must be interpreted with other blood and flow-cytometry findings."]

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

Key facts at a glance

LOINC
33662-8
Short code
RBC CD59 deficient NFr
Synonyms
RBC CD59 deficient NFr
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
4.2
Ref high
5.9
Critical range
2 N/A – 7 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85041
SNOMED
900000000000003001
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 the test measures

The test identifies red blood cells with reduced or absent CD59 on their surface. The reported fraction estimates how many circulating red cells show this deficiency.

How the test is performed

A blood sample is analyzed, usually by flow cytometry. Because red cells can lose normal surface proteins during storage or sample handling, properly handled specimens and appropriate controls are important.

Why CD59 deficiency matters

CD59 normally prevents complement from damaging red blood cells. Without adequate CD59, red cells may be destroyed by the complement system, causing hemolytic anemia, hemoglobin in the urine, blood clots, or symptoms related to low blood counts.

How results are interpreted

A higher fraction of CD59-deficient red cells suggests a larger abnormal cell population. The result is not specific by itself and is generally interpreted alongside FLAER flow cytometry, complete blood count, hemolysis markers, and the clinical picture.

Reference range

Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A

Specimen: whole-blood

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CD59-deficient RBC fraction

Frequently asked questions

Does a positive result mean I have PNH?
Not necessarily. It shows that some red blood cells have deficient CD59, but PNH usually requires additional evidence of an abnormal blood-cell clone and compatible clinical or laboratory findings.
Is this the same as a FLAER test?
No. CD59 and FLAER detect different but related features of the same complement-sensitive blood-cell population. FLAER is generally part of the recommended diagnostic flow-cytometry panel, and CD59 testing can provide additional information.
What if the result is negative?
A negative result means no significant CD59-deficient red-cell population was detected by the test. However, very small abnormal populations or poor specimen handling can affect detection, so the result should be considered with the laboratory's findings and other tests.
  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