Diagnostic Methods (continued)

Non-Culture Tests

Non-culture tests are based on the detection of specific components of the bacterial cell (e.g., particular proteins, ribosomes, nucleic acid sequences, and lipopolysaccharides). These bacterial components can be from either a live cell or from dead cells. Because non-culture tests are approved for many but not all anatomical sites, care must be taken in reviewing the list of approved sites listed in the manufacturer’s package insert for a particular test.

Based on performance, non-culture tests can be categorized as:

1. Nucleic Acid Amplification Tests (NAATs)
2. Non-Amplification Tests

Nucleic Acid Amplification Tests (NAATs):

NAATs amplify nucleic acid sequences (either DNA or RNA) that are specific for the organism being detected. Like other non-culture tests, NAATs do not require live organisms. NAATs are FDA-cleared for urine in men and women, urethral swabs in men and endocervical swabs in women and some tests are cleared for vaginal swabs. Presently, NAAT testing of oropharyngeal and rectal specimens is not recommended.

Several NAATs are commercially available for the detection of C. trachomatis: Polymerase Chain Reaction-PCR (Roche Amplicor®); Transcription Mediated Amplification-TMA (Gen Probe AmpCT, APTIMA®); Strand Displacement Amplification– SDA (Beckton Dickinson ProbeTec®).

Non-Amplification Tests

Non-culture, non-amplification tests include a variety of antigen detection and nucleic acid hybridization methods. These include:

• Enzyme-immuno assays (EIA),
• Direct fluorescent antibody tests (DFA), and
• Nucleic acid hybridization tests, a distinct non-NAAT methodology that detects C. trachomatis-specific DNA or RNA sequences in rRNA, genomic DNA, or plasmid DNA.

None of these non-amplified test methods require live organisms. Further, these methods are less expensive than culture or NAATs and less technically demanding than culture. A disadvantage of these tests is that, with a few exceptions, they have sensitivities that range from 50%-75%.

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