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Serum or plasma concentration of a substance measured by immunoassay (e.g., antibody or protein marker)

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

This test measures the amount of a specific substance in your blood, often used to detect or monitor certain conditions like infections, autoimmune diseases, or protein abnormalities.

Quick summary

["This test helps doctors understand if your body is producing or losing certain substances at unusual levels."]

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

Key facts at a glance

LOINC
98364-3
Short code
XR SIJ-R AP+Obl
Synonyms
XR SIJ-R AP+Obl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr
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

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if they suspect an infection, inflammation, or an autoimmune condition. It could also be used to check for protein-related disorders or to monitor treatment progress for conditions like kidney disease or liver issues.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for a few hours if the test involves a specific analyte related to blood sugar or fats. Bring any medications you’re currently taking to your appointment.

During the Test

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch or discomfort, but it usually only takes a few minutes. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results can vary widely depending on the specific substance being tested. Your provider will compare the results to your health history and other tests to determine what they mean for you. High or low levels may indicate underlying health concerns that need further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Frequently asked questions

What does this test measure?
This test measures the concentration of a specific substance in your blood, often used to identify or track conditions such as infections, immune system activity, or protein-related disorders. The exact substance tested depends on the clinical indication and may include antibodies, proteins, or other biomarkers.
Can I eat or drink before this test?
Generally, no specific dietary restrictions apply unless your test involves substances like glucose or lipids. Always follow your healthcare provider’s instructions for the best results.
How long will I need to wait for my results?
Results can be available within a few hours to several days, depending on the lab and the specific test. Your provider will contact you once they are ready to discuss the findings with you.
  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