Test Id : CHLAP

For suspected Chlamydia trachomatis infection, order either CTRNA / Chlamydia trachomatis, Nucleic Acid Amplification, Varies or CGRNA / Chlamydia trachomatis and Neisseria gonorrhoeae, Nucleic Acid Amplification, Varies.

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.6 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.

If not ordering electronically, complete, print, and send an Infectious Disease Serology Test Request (T916) with the specimen.

0.3 mL

Aiding in the clinical diagnosis of Chlamydia pneumoniae or Chlamydia psittaci infection

Members of the family Chlamydiaceae are small, nonmotile, gram-negative, obligate intracellular organisms that grow in the cytoplasm of host cells. While there are at least 9 species within the Chlamydia genus, 3 are clinically significant, including Chlamydia trachomatis, Chlamydia pneumoniae and Chlamydia psittaci.

The chlamydial life cycle can be divided into 2 distinct phases: an 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.

C 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.

C pneumoniae (formerly known as Taiwan acute respiratory agent and, more recently, as Chlamydophila 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. C pneumoniae is responsible for approximately 10% of pneumonia cases.

Chlamydia pneumoniae

IgM: <1:10

IgG: <1:64

Chlamydia psittaci

IgM: <1:10

IgG: <1:64

IgM

Chlamydia pneumoniae and Chlamydia psittaci

> or =1:10

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

<1:10

IgM endpoint titers below 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.

IgG:

C pneumoniae

> or =1:512

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

> or =1:64 and <1:512

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

<1:64

IgG endpoint titers below 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.

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

C psittaci

> or =1:64

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

<1:64

IgG endpoint titers below 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.

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

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

During a primary Chlamydia infection, the early antibody response may be cross-reactive with multiple Chlamydia species.

This assay does not report antibodies detected against Chlamydia trachomatis. Sera from suspected cases of lymphogranuloma venereum (LGV) should be tested by a Lymphogranuloma Venereum Differentiation Antibody Panel. LGV testing is not performed by Mayo Clinic Laboratories; call 800-533-1710 for assistance.

Due to the limited sensitivity and specificity of Chlamydia serologic tests, patients with suspected C trachomatis infection should be tested by a molecular method (eg, CTRNA / Chlamydia trachomatis, Nucleic Acid Amplification, Varies or CGRNA / Chlamydia trachomatis and Neisseria gonorrhoeae, Nucleic Acid Amplification, Varies) to evaluate for current/active infection.

1. Schlossberg D. Psittacosis (due to Chlamydia psittaci). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Elsevier; 2020:2320-2322

2. Hammerschlag MR, Kohlhoff SA, Gaydos CA. Chlamydia pneumoniae. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Elsevier; 2020:2323-2331

The microimmunofluorescent antibody assay is a 2-stage "sandwich" procedure. In the first stage, the patient serum is diluted in phosphate-buffered saline, added to appropriate slide wells in contact with the substrate, and incubated. After incubation, the slide is washed in buffered saline to remove unbound serum antibodies. In the second stage, each antigen well is overlaid with fluorescein-labeled antibody to IgG or IgM. The slide is incubated, allowing antigen-antibody complexes to react with the fluorescein-labeled anti-IgG. After the slide is washed, dried, and mounted, it is examined using fluorescence microscopy. Positive reactions appear as bright apple-green fluorescent elementary bodies with a background matrix of yolk sac. Semiquantitative endpoint titers are obtained by testing serial dilutions of positive specimens.(Schachter J. Chlamydiae [Psittacosis-Lymphogranuloma Venereum-Trachome Group]. In: Lennette E, Balows A, Hausler W, Shadomy H, eds. Manual of Clinical Microbiology. 4th ed. ASM Press; 1985: 856-861; Smith T. Chlamydia. In: Schmidt N, Emmons R, eds. Diagnostic procedures for viral, rickettsial and chlamydial infections. 6th ed. APHA; 1989: 1165-1198)

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This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

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