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Interpretive Handbook

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Test 8142 :
Chlamydia Serology, Serum

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Members of the family Chlamydiaceae are small, nonmotile, gram-negative, obligate intracellular organisms that grow in the cytoplasm of host cells. Two genera of clinical importance are Chlamydia, which includes Chlamydia trachomatis, and Chlamydophila, which includes Chlamydophila pneumoniae and Chlamydophila psittaci. These organisms share many features of bacteria and are susceptible to antibiotic therapy. They are also similar to viruses, requiring living cells for multiplication.

 

The chlamydial life cycle can be divided into 2 distinct phases: a extracellular, nonreplicating, infectious stage and an obligate intracellular, replicating, noninfectious stage. The infectious form, or elementary body (EB), attaches to the target cell membrane and enters the cell via a phagosome. After cell entry, the EB reorganizes into reticulate particles (forming inclusion bodies) and binary fission begins. After 18 to 24 hours, reticulate particles condense to form EBs. These new EBs are released, beginning another infection cycle.

 

Chlamydophila psittaci is the causative agent of psittacosis, a disease characterized by pneumonia, headache, altered mentation, and hepatosplenomegaly. Psittacosis is acquired by airborne transmission from infected birds.

 

Chlamydophila pneumoniae (formerly known as TWAR and, more recently, as Chlamydia pneumoniae) causes pneumonia in humans. It is unique because it is a primary pathogen of humans, is spread from human to human, and apparently has no animal or bird host. Chlamydophila pneumoniae is responsible for approximately 10% of pneumonia cases.

 

Chlamydia trachomatis has been implicated in a wide variety of infections in humans. It is a common cause of nongonococcal urethritis and cervicitis, and many systemic complications of chlamydial infections have been described. In females, this organism is a cause of pelvic inflammatory disease, salpingitis, and endometritis. In males, epididymitis and Reiter's syndrome occur. Lymphogranuloma venereum is a sexually transmitted infection caused by Chlamydia trachomatis. It presents with a transient primary genital lesion followed by suppurative regional lymphadenopathy. Occasionally, severe proctitis or proctocolitis may develop. Chlamydia trachomatis also causes ophthalmologic infections, such as trachoma (rare in the United States), adult inclusion conjunctivitis and inclusion conjunctivitis in neonates. These disorders have traditionally been diagnosed by cytologic detection or culture. However, molecular detection methods (CTRNA / Chlamydia trachomatis by Nucleic Acid Amplification (GEN-PROBE) may now represent a more sensitive diagnostic approach.

 

Fitz-Hugh and Curtis syndrome (perihepatitis) has been associated with chlamydiae.

Useful For Suggests clinical disorders or settings where the test may be helpful

As an aid in the clinical diagnosis of chlamydial infections

Interpretation Provides information to assist in interpretation of the test results

IgG:

Chlamydophila pneumoniae

> or =1:512

IgG endpoint titers of > or =1:512 are considered presumptive evidence of current infection.

 

<1:512 and > or =1:64

A single specimen endpoint titer of > or =1:64 and <1:512 should be considered evidence of infection at an undetermined time. A second specimen drawn 10 to 21 days after the original draw should be tested in parallel with the first. If the second specimen exhibits a titer > or =1:512 or a 4-fold increase over that of the initial specimen, current (acute) infection is indicated. Unchanging titers >1:64 and <1:512 suggest past infection.

 

<1:64

IgG endpoint titers <1:64 suggest that the patient does not have a current infection. These antibody levels may be found in patients with either no history of chlamydial infection or those with past infection whose antibody levels have dropped below detectable levels.

 

Chlamydophila pneumoniae antibody is detectable in 25% to 45% of adults tested.

 

Chlamydophila psittaci and Chlamydia trachomatis

> or =1:64

IgG endpoint titers of > or =1:64 are considered presumptive evidence of current infection.

 

<1:64

IgG endpoint titers <1:64 suggest that the patient does not have a current infection. These antibody levels may be found in patients with either no history of chlamydial infection or those with past infection whose antibody levels have dropped below detectable levels.

 

IgM

Chlamydophila pneumoniae, Chlamydophila psittaci, and Chlamydia trachomatis

> or =1:10

IgM endpoint titers of > or = 1:10 are considered presumptive evidence of infection.

 

<1:10

IgM endpoint titers <1:10 suggest that the patient does not have a current infection. These antibody levels may be found in patients with either no history of chlamydial infection or those with past infection whose antibody levels have dropped below detectable levels.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Anti-chlamydial IgG can persist for years. All results from chlamydial serologies must correlate with clinical history and other data available to the physician.

 

Specimens drawn too early during primary infection may not contain detectable antibodies. If chlamydial infection is suspected, a second specimen should be drawn 10 to 21 days later and tested in parallel with the original specimen.

 

During a primary Chlamydia infection, the early antibody response is crossreactive with multiple Chlamydia species. Cross-reactivity may also occur due to exposure to more than 1 Chlamydia species.

 

Due to the unique subspecies-specific antigen on the Chlamydophila psittaci organisms, this assay for psittacosis is not expected to detect an antibody response in all cases. Sera from suspected cases of psittacosis should also be screened by complement fixation for detection of chlamydial group antigens. Complement fixation is not performed by Mayo Medical Laboratories; contact Mayo Medical Laboratories for further assistance.

 

Chlamydia micro-immunofluorescent antibody assay utilizes serotypes D-K of Chlamydia trachomatis. Sera from suspected cases of lymphogranuloma venereum should also be screened by complement fixation for detection of chlamydial group antigens. Complement fixation is not performed by Mayo Medical Laboratories; contact Mayo Medical Laboratories for further assistance.      

 

Due to the limited sensitivity and specificity of Chlamydia serologic tests, patients with suspected Chlamydia trachomatis infection should be tested by a molecular method (eg, CDNA / Chlamydia trachomatis by Nucleic Acid Amplification) when clinical manifestations are present.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Chlamydophila pneumoniae

IgG: <1:64

IgM: <1:10

 

Chlamydophila psittaci

IgG: <1:64

IgM: <1:10

 

Chlamydia trachomatis

IgG: <1:64

IgM: <1:10

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Movahed MR: Infection with Chlamydia pneumoniae and atherosclerosis: a review. J South Carolina Med Assoc 1999;95:303-308

2. Smith T: Chlamydia. In Diagnostic Procedures for Viral, Rickettsial and Chlamydial Infections. Sixth edition. Edited by N Schmidt, R Emmons. Washington, DC, APHA, 1989, pp 1165-1198

3. Sheffield PA, Moore DE, Voigt LF, et al: The association between Chlamydia trachomatis serology and pelvic damage in women with tubal ectopic gestations. Fertil Steril 1993;60:970-975


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