DFA, EIA, PCR, LCR and Other Technologies: What Tests Should Be Used for Diagnosis of Chlamydia Infections?

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Abstract
For many years, isolation in tissue culture (TC) was considered the test of choice for diagnosis of Chlamydia trachomatis infection. Non-culture tests, such as direct fluorescent antibody (DFA) and enzyme immunoassay (EIA) which detected chlamydial antigens in clinical specimens, made chlamydia diagnostic tests more widely available. DFA and EIA were less sensitive than TC and had some false positive results which compromised our ability to use these tests in low prevalence settings. Direct nucleic acid probes are available, but do not appear to be more sensitive than EIA. It was only with the introduction of amplified DNA tests [polymerase chain reaction (PCR) and ligase chain reaction (LCR)] that non-culture tests became available that were actually more sensitive than TC. Unfortunately these tests are also more expensive than the antigen detection methods. Until there is a fairly sophisticated cost benefit analysis or a change in the pricing of these tests, it seems obvious that TC will remain the best choice where medical/legal implications are important, DFA will probably remain a widely used tests for laboratories that process relatively small numbers of specimens and EIAs will play a role where cost is major factor and large numbers of specimens require bulk processing. Where they are affordable, the amplified DNA tests are to be preferred as they are far more sensitive than these other non-culture tests.