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Chlamydia trachomatis DNA, SDA

Chlamydia trachomatis DNA, SDA

Test Highlight

Chlamydia trachomatis DNA, SDA


Clinical Use

  • Screen for Chlamydia trachomatis infection

  • Diagnose C trachomatis infection

Clinical Background

C trachomatis infection is the most common bacterial sexually transmitted infection in the United States, with approximately 3 million new cases annually. About half of C trachomatis infections in men and 75% in women are asymptomatic. Left untreated, 20% to 40% of women with chlamydia may develop pelvic inflammatory disease (PID), which can lead to infertility, ectopic pregnancy, and chronic pelvic pain.

Screening asymptomatic women for chlamydia can decrease the incidence of PID and, possibly, the prevalence of chlamydial infection. The US Preventive Services Task Force recommends routine chlamydia screening for all sexually active women 25 years of age or younger, as well as for pregnant women and others at increased risk.

Of the available chlamydia tests, culture has the highest specificity and is the only method valid for medico-legal purposes. However, it requires tightly controlled conditions to achieve high sensitivity. Nucleic acid amplification tests (NAATs) using technologies such as strand displacement amplification (SDA) are typically more sensitive than culture, can use urine as a specimen, and provide greater sensitivity and specificity than other non-culture assays. Because of assay sensitivity and ease of specimen collection, the CDC now recommends NAATs for chlamydia screening in men and women (MMWR. 2002;51(RR-15):1-38).


In this assay, target DNA is amplified by isothermal strand displacement amplification (SDA) using 2 enzymes (DNA polymerase and a restriction endonuclease). Amplification products are detected simultaneously via fluorescence energy transfer from labeled probes.

Alias: ProbeTec™

Interpretive Information

Positive results should be considered presumptive evidence of infection. Negative results are highly specific for lack of C trachomatis infection. The clinical sensitivity and specificity of this assay depend on the presence or absence of clinical symptoms, the patient‘s sex, and the type of specimen tested. Seminal fluid, mucus, lubricants, and common ointments do not appear to interfere with the assay. Samples containing leukocytes or blood (any amount of blood in urine or >5% in swabs) may give false-negative results. Additional testing is recommended if false-positive or false-negative results could lead to adverse medical, social, or psychological consequences.


Content reviewed 07/2013

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