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What is being tested?

The test is looking for evidence of infection by the bacterium Chlamydia trachomatis, the most common bacterial sexually transmitted infection (STI) in Australia. Diagnosing and treating chlamydia is very important to prevent long-term complications and spread of the infection to others.

Chlamydia is generally transmitted through sexual contact (oral, vaginal or anal) with an infected partner. Young, sexually active people are particularly at risk, with 80% of reported cases in 15-29 year olds. Other risk factors include having multiple sex partners, coinfection or previous infection with another STI, and not using barrier contraception consistently. An infected mother can spread the disease to her baby during childbirth. These babies are in danger of developing pneumonia (a lung infection) or conjunctivitis, an inflammation that can threaten eyesight.

About 70-80 per cent of infected women and half of infected men have no symptoms; some may experience only mild symptoms. For women, symptoms, if they occur, include bleeding between menstrual periods and after sexual intercourse, abdominal pain, painful intercourse and an abnormal vaginal discharge. For men, symptoms include pus or milky discharge from the penis and inflammation of the prostate (prostatitis) or of the rectal area (proctitis). Both sexes can experience painful or frequent urination.

Chlamydia is treated with a course of antibiotics, but can cause severe reproductive and other health problems if left untreated. If untreated, around one third of women may develop pelvic inflammatory disease (PID) from infections that start on the cervix but that can spread to the fallopian tubes and ovaries. This can cause infertility and increase the risk of potentially life-threatening tubal (ectopic) pregnancy. Women who are infected and pregnant may experience heavy bleeding before delivery and premature rupture of the membranes. Men, too, may become sterile. Both sexes may develop rectal itching or red, swollen, itchy eyes.

How is it used?

The test is used in two ways:

  • to diagnose the cause of symptoms, and
  • to screen sexually active people for the bacterium.

A definitive diagnosis is important because chlamydia can resemble gonorrhoea, and the two infections require different antibiotic treatment.

Nucleic acid amplification based techniques - e.g. polymerase chain reaction (PCR) and ligase chain reaction (LCR) are the most commonly used. They are sensitive, quick and less affected by delays in the transportation of specimens to a laboratory.

When is it requested?

A doctor may request the test if you have symptoms such as vaginal discharge and abdominal pain (for women) or unusual discharge from the penis or pain on urination (for men). However, about 70-80% of infected women and 50% of infected men show no active symptoms. Risk factors for chlamydia infection include age under 30 years, having new or multiple sex partners, having sex with someone who has other partners and not using barrier contraceptives, such as condoms. You may wish, or your doctor may suggest, that you be screened for the infection if you have any these risk factors.

What does the result mean?

A positive test indicates an active infection that requires treatment with a course of antibiotics.

Is there anything else I should know?

Chlamydia is often called ‘the silent epidemic’ because infections are so prevalent yet many people do not know that they are infected. Chlamydia is especially widespread among young people under the age of 30.

Chlamydia is easily treated, but if left untreated, it can cause severe reproductive and other health problems. If you are infected, your sexual partner(s) should also be tested and treated as well.

People who are infected have a higher risk of developing other sexually transmitted diseases, including a 2 to 5 times greater risk of acquiring HIV if exposed to it.

The diagnosis of a sexually transmitted disease should not be ruled out if the test is negative; patients' clinical symptoms and history should also be considered.

Common questions

  • What are the symptoms of chlamydia?

Most infected people have no symptoms, so they do not seek treatment. For women, symptoms (if they occur) include bleeding between menstrual periods and after sexual intercourse, abdominal pain, painful intercourse and an abnormal vaginal discharge. For men, symptoms include pus or milky discharge from the penis. Both sexes can experience painful or frequent urination.

  • What will happen if I don’t get treated?

If left untreated, women may develop pelvic inflammatory disease (PID) from lesions that start on the cervix but that can spread to the fallopian tubes and ovaries. This can cause infertility and increase the risk of tubal or ectopic pregnancy. Women who are infected and pregnant may experience heavy bleeding before delivery and premature rupture of the membranes. Men, too, may become sterile. Both sexes may develop rectal itching and red, swollen, itchy eyes.

  • How is chlamydia transmitted?

It is generally transmitted through sexual contact (oral, vaginal or anal) with an infected partner. An infected mother can spread the disease to her baby during childbirth. These babies are in danger of developing conjunctivitis (an inflammation that can threaten eyesight) and pneumonia.

  • How is it treated?

Chlamydia can be easily treated with a course of antibiotics.

  • How can it prevented?

Sexually active men and women can reduce their risk of chlamydia by reducing their numbers of partners and by using condoms correctly and consistently during sexual intercourse. Another important prevention strategy is regular testing of sexually active people for symptomatic or asymptomatic infection. Testing is recommended if there are symptoms, once people become sexually active, when they change sexual partners or when they start a new relationship.

Last Updated: Thursday, 1st June 2023

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