Interpretation

IgM

Chlamydia pneumoniae and Chlamydia psittaci

≥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

≥1:512

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

≥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

≥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.