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: Reagin Antibody, Cerebrospinal Fluid, Qualitative

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

: This test looks for reagin antibodies in cerebrospinal fluid (CSF), the fluid that surrounds the brain and spinal cord. It is most often used as part of the evaluation of neurosyphilis, a syphilis infection that has spread to the nervous system.

Quick summary

[": A qualitative CSF reagin result helps show whether syphilis-related antibodies are present in the spinal fluid."]

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

Key facts at a glance

LOINC
22459-2
Short code
Reagin Ab CSF Ql
Synonyms
Reagin Ab CSF Ql
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

: What Is Being Tested

: The test detects reagin antibodies—antibodies that can appear when a person is infected with syphilis—in a sample of cerebrospinal fluid. It is a qualitative test, meaning the result is typically reported as positive/reactive or negative/nonreactive rather than as a precise number.

: How the Sample Is Collected

: Cerebrospinal fluid is collected through a lumbar puncture (spinal tap), in which a needle is placed in the lower back to draw fluid. This is a specialized procedure performed by a clinician, and the fluid is then sent to the laboratory for analysis.

: What the Result Means

: A nonreactive result means reagin antibodies were not detected in the CSF. A reactive result means they were detected, which can support concern for neurosyphilis. Because reagin tests can sometimes give false positives or false negatives, results are interpreted together with symptoms, blood tests, and sometimes other CSF tests.

: How It Fits Into Care

: CSF reagin testing is not a routine screening test for everyone. It is usually ordered when a person has syphilis and symptoms or signs suggesting nervous system involvement, or when a clinician needs additional information about possible neurosyphilis.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

: CSF Reagin

Frequently asked questions

: Does a reactive CSF reagin test always mean I have neurosyphilis?
: No. A reactive result supports concern for neurosyphilis but is not definitive by itself. Other findings and clinical context are needed, and your clinician will interpret the result along with additional tests and symptoms.
: Is a spinal tap required for this test?
: Yes. The test measures reagin antibodies in cerebrospinal fluid, so a CSF sample must be collected by lumbar puncture.
: Can this test be done from a blood sample instead?
: No. Blood tests for syphilis are different tests and are interpreted separately. This test specifically evaluates cerebrospinal fluid, so it requires a CSF specimen.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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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