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Chlamydia Antibody (Serum) – Qualitative Immunoassay

Published: August 9, 2026Updated: August 15, 2026

This test detects antibodies in your blood that may indicate past or current infection with *Chlamydia trachomatis*, a common sexually transmitted bacterium.

Quick summary

["A positive result suggests exposure to chlamydia, but further testing may be needed to confirm active infection."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
5084-9
Short code
CHLSPAB
Synonyms
Chlamydia Ab Titr Ser IF
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) - Red-top or tiger-top tube with gel separator
Units
N/A
Ref low
16
Ref high
1
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Immunofluorescence (IFA)
CPT
86631
SNOMED
395128002
Specimen volume
1.0-2.0 mL of serum (minimum 0.5 mL)
Stability
Serum separated and stored at 2-8°C: 7 days; Frozen at -20°C or below: 30 days; Avoid repeated freeze-thaw cycles. For long-term storage, aliquot and store at -70°C.
Hemolysis max
200
Lipemia max
150
Icterus max
50
TAT
48–96 hours
Order
routine

What Does This Test Measure?

The test looks for antibodies produced by your immune system in response to *Chlamydia trachomatis*. Antibodies are proteins your body makes to fight infections. This test is qualitative, meaning it only tells you if antibodies are present (positive) or not (negative), without showing how much is present.

Why Might You Need This Test?

Doctors may order this test if you have symptoms like unusual discharge, pain during urination, or if you’ve been exposed to chlamydia. It’s also sometimes used as a screening test for sexually transmitted infections (STIs) in certain groups.

What Does a Positive Result Mean?

A positive result means your body has detected antibodies to chlamydia, which could indicate past infection or exposure. However, this alone does not confirm an active infection—additional testing (like a nucleic acid amplification test) would be needed to diagnose an active chlamydia infection.

What Does a Negative Result Mean?

A negative result means no detectable antibodies were found at the time of testing. This does not guarantee you are not infected now, as it may take time for your body to produce antibodies after exposure.

Reference range

Titer < 1:16: Negative (No detectable antibodies); Titer 1:16-1:64: Equivocal/Borderline (Repeat testing in 2-4 weeks recommended); Titer ≥ 1:128: Positive (Indicates prior exposure or current infection with Chlamydia species)N/A

Specimen: serum

No special patient preparation is required. However, patients should inform their healthcare provider about any current antibiotic therapy, as recent antimicrobial treatment may affect antibody levels. Acute and convalescent serum samples (drawn 2-4 weeks apart) are recommended for optimal diagnostic interpretation of seroconversion.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Chlamydia Antibody Screen (Serum)

Frequently asked questions

Chlamydia is a common bacterial infection that can cause serious health problems if untreated, such as pelvic inflammatory disease (PID) in women, infertility, or long-term complications in both sexes. Early detection through antibody screening helps guide treatment and prevent complications.
This test is not used to diagnose an active infection but may be part of a broader STI screening panel. If you have symptoms or risk factors, your doctor may recommend additional testing.
If I get a positive antibody result, will I automatically need treatment?
No. A positive antibody test alone does not mean you have an active infection. Your doctor will likely order further testing (like a PCR test) to confirm if you have an active chlamydia infection, which would require treatment.
Can I get false positives or false negatives with this test?
Yes. False positives can occur if you’ve been previously exposed or vaccinated. False negatives are less likely but can happen if testing is done too early after exposure or if the infection is very mild. Follow-up testing may be needed for unclear 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 15, 2026. · Read our editorial policy