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Chlamydia Detection

Chlamydia trachomatis infection is the most common sexually transmitted disease in the United States and Europe.  Chlamydia causes an estimated four to five million infections each year in the United States.  Men, women, and infants are affected, but women are at greatest risk of serious complications.  In women, Chlamydia infections begin as a silent infection of the cervix, which can last up to 21 days.  Ascending disease involves the fallopian tubes and ovaries, producing pelvic inflammatory disease.  Chlamydia infections are a leading cause of infertility and ectopic pregnancy.  About 70% of infected mothers transmit Chlamydia to the newborn during birth.  Infected infants are at increased risk of developing pneumonia and conjunctivitis. 

The U.S. Preventive Services Task Force issued updated guidelines in 2014 for Chlamydia trachomatis infection screening. The recommendations state that primary care physicians should routinely screen all sexually active women age 24 years and younger and in older women who are increased risk for infection. Risk factors include new or multiple sex partners, a sex partner with concurrent partners, a sex partner with a sexually transmitted infection; inconsistent condom use among persons who are not in mutually monogamous relationships; previous or concurrent STI; and exchanging sex for money or drugs.

Repeat screening is recommended 3 months after treatment because one in five women with chlamydial infection becomes reinfected within 1 year after treatment.  Reinfection is associated with increased risks for ectopic pregnancy and pelvic inflammatory disease.

Nearly 70% of male partners of women with chlamydial infection are also infected. Chlamydial urethritis is 2.5 times more common than gonococcal urethritis in men. In addition, it causes about half of the estimated annual 500,000 cases of acute epididymitis. Chlamydial proctitis and pharyngitis occur in homosexual males.  

Sexual partners of women who received a diagnosis of Chlamydial infection should be screened if sexual contact occurred within 60 days of the diagnosis or development of symptoms. Screening should also be considered for at risk sexually active men including; men who attend clinics for sexually transmitted diseases, incarcerated men, men who have sex with men). Routine screening of all men is not recommended by CDC.

Nucleic acid amplification tests, such as polymerase chain reaction (PCR), are the preferred method for detecting Chlamydia infection. Sensitivity of  PCR on specimens collected from genitourinary sites has ranged from 86% to 100% in studies without major limitations. PCR is approved by the U.S. Food and Drug Administration for use on urogenital sites, including male and female urine; clinician-collected endocervical, vaginal, and male urethral specimens; and self-collected vaginal specimens in clinical settings. The Centers for Disease Control and Prevention (CDC) considers vaginal swabs to be the preferred specimen type, because nucleic acid amplification tests on vaginal swabs perform as well as those on cervical swabs and they can be more easily self-collected. A first-catch urine specimen is also acceptable but may fail to detect up to 10% of infections.

Swab specimens should be submitted in M4 transport media and refrigerated. Urine specimens should consist of the first 10 to 50 mL of the urine stream. Urine should be submitted in a clean container without preservatives, and may be transported at room temperature within 24 hours of collection. Excessively bloody specimens may cause false positive. Excessive mucus in endocervical samples may cause false negative results.

Results are reported as positive or negative for Chlamydia by PCR.

LeFevre, ML on behalf of the U.S. Preventive Services Task Force, Screening for Chlamydia and Gonorrhea: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med 2014;161 (12) 902


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