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Laboratory Report: Laboratory Diagnosis of Chlamydia trachomatis Infections

Posted April 1, 2005

Chlamydia trachomatis is the most common bacterial sexually transmitted disease worldwide and the sequelae are substantial. The majority (50-80%) of people infected are unaware of the infection because they do not have symptoms. Consequently, screening plays an important role in diagnosing and treating this infection. In 2001, the US Preventive Services Task Force recommended that all sexually active women under the age of 25 and women at increased risk for infection should be screened for C. trachomatis. There is no evidence for direct screening of asymptomatic men and infants.

Chlamydia infections often involve the urethra or rectum, as well as the cervix in women. In infants born to infected mothers, manifestations include conjunctivitis and pneumonia. Ascending infection, from the cervix in women and the urethra in men, results in pelvic inflammatory disease (PID) and epididymitis, respectively. These conditions cause infertility, and in women, PID is associated with ectopic pregnancy, a life-threatening condition.

An overwhelming number of laboratory tests are available for C. trachomatis, which will be briefly reviewed here. The most recent and complete review of laboratory methods can be found at




Rapid Tests

















FDA approved sites for use

Cervix, urethra, pharynx, rectum, conjunctiva

Cervix, urethra, pharynx, rectum, conjunctiva

Cervix, urethra, conjunctiva

Cervix, urethra

Cervix, urethra, conjunctiva

Cervix, urethra, urine

Turn around time

2-4 days

1-2 days

1-3 days

30 minutes

1-3 days

1-3 days

Confirmatory testing*



Competitive assay, DFA, NAA, Culture

DFA, NAA, Culture

Competitive assay, NAA, Culture

Repeat test, Culture


Labor intensive;

Only current acceptable test for medicolegal purposes

Can’t be done in large quantities; Labor intensive; Usually used as confirmatory test

Automation possible

Based on membrane capture or latex immunodiffusion;

Presumptive positive only, must confirm

Not all tests use SA;

Automation possible


Based on PCR, TMA or SDA;

Automation possible

DFA – Direct Fluorescent Antibody, EIA – Enzyme Immunoassays, NAP – Nucleic Acid Probe (SA – Signal Amplification),

NAA – Nucleic Acid Amplification, PCR – Polymerase Chain Reaction, TMA – Transcription Mediated Amplification, SDA – Strand Displacement Amplification

* Confirmatory testing is not always necessary. Decision to perform is based on the prevalence of disease in the patient population of testing laboratory.

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NewsPath® Editor: Megan J. DiFurio, MD, FCAP
This newsletter is produced in cooperation with the College of American Pathologists Public Affairs Committee and may be reproduced in whole or in part as a service to the medical community. Copyright © 2006 by the College of American Pathologists.
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