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Purine Nucleoside Phosphorylase (PNP), Cerebrospinal Fluid — Catalytic Concentration

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

Measures PNP enzyme activity in cerebrospinal fluid to help evaluate rare inherited PNP deficiency and related immune or neurologic findings.

Quick summary

["This test measures PNP enzyme activity in spinal fluid and may help identify PNP deficiency."]

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

Key facts at a glance

LOINC
35141-1
Short code
PNP CSF-cCnc
Synonyms
PNP CSF-cCnc
Category
urine
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 this test?

Purine nucleoside phosphorylase, or PNP, is an enzyme involved in purine metabolism and immune-cell function. This test measures PNP activity in cerebrospinal fluid, the fluid surrounding the brain and spinal cord.

Why might I need this test?

This uncommon test may be ordered when symptoms suggest purine nucleoside phosphorylase deficiency, a rare inherited condition. It may be considered in people with recurrent infections, developmental concerns, or unexplained neurologic problems.

How is the test performed?

Cerebrospinal fluid is usually collected through a lumbar puncture, also called a spinal tap. The laboratory then measures the amount of PNP enzyme activity in the fluid.

How do I prepare for the test?

Fasting is generally not required, but you should tell the healthcare provider about medicines, allergies, bleeding problems, or possible pregnancy. A lumbar puncture requires positioning, local anesthetic, and consent from the healthcare professional performing the procedure.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Lower-than-expected PNP activity may support a diagnosis of purine nucleoside phosphorylase deficiency, particularly when immune, developmental, or neurologic findings are also present. Results must be interpreted with the symptoms, medical history, and other laboratory tests because low activity can have other causes.

Short name

CSF Purine Nucleoside Phosphorylase Activity

Frequently asked questions

What does PNP stand for?
PNP stands for purine nucleoside phosphorylase, an enzyme that helps break down purines and supports normal immune-cell function.
Why is PNP measured in cerebrospinal fluid?
Measuring PNP in cerebrospinal fluid can help evaluate rare inherited enzyme disorders that may affect the immune system and nervous system.
Does this test require fasting or special preparation?
Fasting is usually unnecessary. Tell your healthcare provider about medications, bleeding risks, allergies, and possible pregnancy before the spinal tap.
  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