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Chlamydia Testing

Last updated Oct. 11, 2015

Photomicrograph of Chlamydia trachomatis taken from a urethral scrape specimen.


What are the other Names for this Test? (Equivalent Terms)

  • Chlamydia trachomatis by Amplified Detection
  • Chlamydia trachomatis by Direct Antigen Detection (DFA)
  • Chlamydia trachomatis Culture

What is Chlamydia Testing? (Background Information)

Chlamydia infection is a very common STD (sexually transmitted disease) caused by chlamydia trachomatis bacteria, commonly affecting people in the 15-25 age group. The bacterium spreads via sexual contact with an infected individual and due to factors, such as:

  • Having multiple sex partners
  • Having other sexually transmitted infections
  • Previous history of sexually transmitted infections
  • Inconsistent condom use
  • Having a same-sex partner (especially, men having sex with men)

In a majority of infected women and at least 50% of infected men, chlamydia produces no symptoms. In others:

  • Women may experience abdominal pain, burning urination, vaginal discharge, bleeding in-between periods or after sex, painful intercourse, or infertility
  • Men may have discharge from penis, burning urination, inflammation of prostate (prostatitis), or inflammation of rectal area (proctitis)
  • In newborns, chlamydia may cause redness/discharge from the eyes (conjunctivitis)

A sample of cells or discharge, collected from the infected area is used to diagnose chlamydia. A number of tests maybe performed on the sample, to arrive at a diagnosis.The physician decides which test is to be used, in any given scenario. The tests include:

  • Nucleic acid amplification test (NAAT): It is the most sensitive (capable of correctly identifying an individual with the disease) and specific (capable of correctly identifying an individual, free from the disease) test available. This test works by even detecting small amounts of chlamydia DNA (genetic material) in the sample, by amplifying or increasing its amount, to aid detection
  • DNA probe test: This test also works by detecting chlamydia DNA in the sample; however, it is not as sensitive as NAAT
  • Direct fluorescent antibody (DFA) test: In this test chlamydial antigens (substances that activate the body’s immune system and react with antibodies) are detected from the sample
  • Culture: In a culture, the sample is inoculated on a medium (substance that is nutritive to bacteria) and bacteria in the sample are allowed to grow and multiply. This test takes about 5-7 days

What are the Clinical Indications for performing the Chlamydia Testing?

Indications for Chlamydia Testing include:

  • Screening of sexually active women under 25 years and all others (sexually active women) who are at an increased risk of contracting STDs (as per guidelines laid down by the Centers for Disease Control and Prevention (CDC) & American College of Obstetricians and Gynecologists; this screening is to be done annually)

Note: The US Preventive Services Task Force recommends Chlamydia Screening for all women under age 24 years, or those older than 24 years and having risk factors for the disease.

  • Risk factors for chlamydia include:
    • Multiple sexual partners
    • Presence of other sexually transmitted infections
    • Previous history of chlamydia infection
    • Not practicing safe sex, irregular condom use
    • Commercial sex workers
    • Becoming sexually active at an early age
    • Having same sex partners; especially man to man sex

According to the guidelines laid down by CDC, pregnant women are recommended to undergo screening at first antenatal visit and later, again after 3-6 months, if they test positive. For women under 25 years of age, a second testing is routinely advised in the third trimester of pregnancy.

  • To diagnose the cause of symptoms (below), when a physician suspects STD as a probable cause:
    • In a woman: Abdominal pain, burning urination, vaginal discharge, bleeding in between periods or after sex, painful intercourse, or infertility
    • In a man: Discharge from penis, burning urination, inflammation of prostate/rectal area
  • Victims of sexual assault are advised to undergo culture for chlamydia
  • Newborns with conjunctivitis (indications include red eyes, discharge from the eyes)

How is the Specimen Collected for Chlamydia Testing?

Sample required:

  • Discharge, or  direct sample of cells from the area considered infected (may be urethra in men, cervix in women, anus, eyes, or sometimes even from the throat)
  • Urine sample (called first catch urine sample)

Process:

  • To obtain a direct sample, a swab or brush is used to gently collect cells from the suspicious areas
  • Urine sample: The first few drops of the urine stream is collected for testing

Preparation required:

  • Women who are going to have a direct sampling of cells from cervix for Chlamydia Testing should not use vaginal creams or douches, for 24 hours prior to testing
  • It is advised not to urinate for 2 hours, before giving a urine sample for testing
  • It is also necessary to inform the physician about any current antibiotic use, as this may affect the test results

What is the Significance of the Chlamydia Testing Result?

The test may be reported as, either chlamydia positive or chlamydia negative.

  • Individuals testing positive for chlamydia are treated with antibiotics. Their sexual partners should also be tested and treated, if found positive
  • A negative test result only indicates that there is no infection at the time of testing. However, regular screening of individuals with high-risk behavior is advised, to detect infection or re-infection, as early as possible

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Any individual, who tests positive for chlamydia infection, should abstain from sex for 7 days, after start of treatment
  • Often, chlamydia can coexist with other STDs, and tests may have to be conducted to detect these as well
  • (In the US) The physician is bound to inform a positive chlamydia test to the state health department. The sexual partners of those testing positive, maybe contacted by the department for testing and treatment

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis. 

What are some Useful Resources for Additional Information?

DoveMed is currently working to bring you additional resources.

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References and Information Sources used for the Article:

http://labtestsonline.org/understanding/analytes/chlamydia/ (accessed on 11/05/2013)

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Nov. 12, 2013
Last updated: Oct. 11, 2015