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Serum/Plasma Opsonin Activity (Throat Swab)

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

This test measures how well your immune system’s proteins help fight off bacteria in throat swab samples. It helps assess immune response to infections like strep throat.

Quick summary

["Helps evaluate immune function in throat infections by testing protein activity against bacteria."]

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

Key facts at a glance

LOINC
18481-2
Short code
S pyo Ag Throat Ql
Synonyms
S pyo Ag Throat Ql
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

The test analyzes opsonins—proteins that tag bacteria for destruction by immune cells—using a throat swab specimen. It detects how effectively these proteins bind and neutralize bacteria in your throat environment.

Why It’s Done

Your healthcare provider may order this test if you have recurrent throat infections, symptoms of immune dysfunction, or if you’re being evaluated for conditions like chronic bacterial infections or immune deficiencies.

How It Works

A swab is collected from your throat to gather bacteria. The sample is then tested for opsonin activity by exposing it to bacterial targets, measuring how well immune proteins tag and clear the bacteria over time.

Preparation Tips

No special preparation is needed. Avoid antibiotics or immune-modifying medications for at least 7 days before testing, as they may affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Throat Swab Opsonin Function Test

Frequently asked questions

Why might my throat swab test show abnormal opsonin activity?
Possible causes include chronic bacterial throat infections, immune system disorders (like HIV or autoimmune diseases), or recent use of antibiotics that suppress immune function. Your provider will discuss findings with you.
How long will I need to wait for results?
Results are typically available within 2–5 business days, depending on lab processing. Your provider will contact you with the final report.
Can I take anything to improve my immune response before testing?
No dietary supplements or immune-boosting products should be taken before testing. Follow your provider’s instructions to ensure accurate results.
  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