Chlamydia Testing Dx

Last updated: November 3, 2014

CPT Codes:  Chlamydia trachomatis, amplified probe technique 87491;  Chlamydia culture 87110

Description: A variety of tests are useful in diagnosing infection or past exposure to chlamydial species (Chlamydia trachomatis, Chlamydia psittaci, Chlamydia pneumoniae and Chlamydia pecorum). C.trachomatis is most prevalent and may give rise to trachoma, lymphogranuloma venereum, urogenital infection, reactive arthritis.  Chlamydial testing carries added importance as half of male and the majority of females who are infected are asymptomatic.

Method: Chlamydial infection is best detected by analysis of specimens taken from urethral, cervical, conjunctival, nasopharyngeal, or rectal swabs. Studies have shown that patient collected specimens are as reliable as physician collected specimens.  Genitourinary specimens are most reliable when not contaminated with urine. In males, urethral swabs should be inserted >2 cm into the urethra. In females, swabs of the cervix/endocervix should be sufficient to collect infected epithelial cells. Serum antibody assays are less reliable. Available tests include:
— Culture: Although this is most definitive, culture is difficult and unreliable; 2- to 7-day turnaround time.
— Nucleic acid amplification tests (NAATs): NAATS are designed to amplify and detect nucleic acid sequences specific for Chlamydia and do not require viable organisms.  Amplification technologies include polymerase chain reaction (PCR),  strand displacement amplification (SDA) or transcription-mediated amplification (TMA) to detect specific chlamydia RNA or DNA sequences.  NAATs are best performed on patients collected specimens (vaginal or urethral swabs are preferred to urine). They have high specificity and good sensitivity that is diminished in low risk populations.   Specimens collection kits are usually provided by the laboratory.
—Serologic tests for IgG or IgA anti-Chlamydia antibodies: may be useful in the diagnosis of systemic infection (i.e., infantile pneumonia, lymphogranuloma venereum, or psittacosis) or the evaluation of recurrent miscarriage, tubal infertility and extrauterine pregnancy.
—Not recommended:  Enzyme immunoassays, nucleic acid probe tests, genetic transformation tests,  complement fixation assays or microimmunofluorescence.

Positive in: More than 50% of patients with reactive arthritis (Reiter ’s syndrome) have positive results, as do those with nongonococcal urethritis, ocular infections, psittacosis, or lymphogranuloma venereum. Acute and convalescent serum titers may be necessary to prove infection. Titers of >1:640 suggest active infection.

Confounding Factors: Recent antibiotic therapy may alter culture but not serologic or PCR results.

Indications: Tests may be useful in patients with suspected reactive arthritis, ocular and urogenital infections, or psittacosis. NAAT, serologic or culture evidence of infection may be an indication for antibiotic therapy.  The role of random population screening for chlamydia has not been established.

Cost: Enzyme immunoassay, $100–120; DNA probe, $60–80; culture, $100–120.

Centers for Disease Control and Prevention. Recommendations for the laboratory-based detection of Chlamydia trachomatis and Neisseria gonorrhoeae--2014. MMWR Recomm Rep. 2014;63:1-19. PMID: 24622331

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