CPT® Code 87542

The CPT® Code 87542 refers to a laboratory test designed for the detection of the infectious agent Legionella pneumophila through the analysis of nucleic acids, specifically DNA or RNA. Legionella pneumophila is a gram-negative bacterium commonly found in aquatic environments, which can lead to serious health issues such as pneumonia, known as Legionnaire’s Disease, or a milder illness resembling influenza, referred to as Pontiac Fever. This test utilizes a direct probe method to identify a unique nucleic acid sequence, termed the target sequence, associated with the L. pneumophila organism, should it be present in a respiratory specimen. The detection process involves the use of a probe that is labeled with either fluorescent or chemiluminescent markers. To perform the test, the sample is treated to release nucleic acids from the target organism, if it exists. The labeled probe then selectively binds to the matching target sequence, forming a stable hybrid. Ribosomal RNA is often the focus of this detection method due to its abundance in microorganisms, as it typically exists in thousands of copies compared to the limited 1-2 copies found in genomic DNA. The sensitivity of the assay is significantly enhanced through an amplified probe technique, which involves exponentially multiplying the target sequence of L. pneumophila DNA or RNA into millions of copies. The polymerase chain reaction (PCR) or reverse transcriptase polymerase chain reaction (RT-PCR) is the most frequently employed amplification technique. Following amplification, the replicated sequences are identified using labeled DNA probes. The quantification aspect of this test, as indicated by the CPT® Code 87542, provides a measurement of the number of microorganisms present in the sample. Quantitative or real-time PCR is typically utilized to amplify the isolated nucleic acid segment and generate a report that documents the absolute or relative amounts of the known nucleic acid sequence at each stage of the testing process.