The Current Procedural Terminology (CPT) system provides a standardized language for reporting medical services and procedures to payers like insurance companies. CPT code 87798 is a specific identifier used by healthcare providers and laboratories to document a particular type of diagnostic test. This code falls within the larger group of codes for pathology and laboratory procedures, specifically those related to microbiology.
The Specific Laboratory Service
CPT code 87798 describes a laboratory procedure for the “Infectious agent detection by nucleic acid (DNA or RNA), not otherwise specified; amplified probe technique, each organism.” This definition indicates a molecular diagnostic test that looks for the genetic material—DNA or RNA—of a pathogen, such as a bacteria, virus, or fungus. The core methodology involves a Nucleic Acid Amplification Test (NAAT), most commonly the Polymerase Chain Reaction (PCR), which significantly multiplies the genetic fragments from the sample. This amplification step makes even minute amounts of a pathogen’s genetic material detectable, offering high sensitivity and specificity.
The “amplified probe technique” refers to the method used to confirm the identity of the amplified genetic material. Specialized probes are designed to bind only to the target organism’s unique sequence, confirming its presence. A laboratory reports this code once for each distinct organism tested using this specific molecular method. This code is considered a “not otherwise specified” (NOS) code, meaning it is used only when a more organism-specific CPT code does not already exist for the pathogen being tested.
Clinical Context and Test Interpretation
The clinical purpose of using CPT code 87798 is to achieve a precise and timely diagnosis when a specific, but less common, infectious agent is suspected. Since the test targets the organism’s unique genetic fingerprint, it can identify pathogens that are difficult or slow to grow using traditional culture-based methods. This molecular approach provides results faster than older techniques, allowing physicians to begin targeted, effective treatment sooner.
For a physician, the result of a test billed under 87798 offers definitive information to guide therapeutic decisions, such as selecting the most appropriate antibiotic or antiviral medication. The NOS nature of the code means the provider has ordered a test for an organism that lacks a standard, highly specified CPT code, suggesting a focused suspicion. If a less-common bacterial infection is suspected, the laboratory uses 87798 to report the NAAT detection of that organism. A positive result confirms the suspected pathogen, enabling a shift from broad-spectrum to narrow-spectrum therapy.
While the code is billed for each organism tested, it is often used when a physician suspects a single organism that lacks a dedicated code, rather than a broad diagnostic panel. Comprehensive panels that test for multiple common pathogens simultaneously typically have their own specific CPT codes. When a physician orders a custom combination of single-organism tests, the lab may bill multiple units of 87798, each representing a different organism.
Administrative and Billing Considerations
From an administrative perspective, CPT code 87798 is categorized as a pathology and laboratory procedure, and it dictates how the performing lab is reimbursed for the service. The payment for this molecular diagnostic test depends heavily on clear documentation that establishes the medical necessity for the procedure. Laboratories must link the CPT code to a corresponding International Classification of Diseases (ICD-10) code that justifies why the specific test was ordered based on the patient’s symptoms or condition.
The use of this NOS code can sometimes present administrative challenges because of its “catch-all” nature. Payers, including insurance companies, prefer to see the most specific CPT code available; therefore, using 87798 when a more precise code exists can lead to claim denials or requests for additional information. To manage the billing process, laboratories may need to utilize specific modifiers, such as Modifier 59, which indicates a “Distinct Procedural Service” when multiple units of 87798 are legitimately billed on the same day for different organisms.
Furthermore, the code is sometimes involved in complex billing scenarios when multiple tests are performed, especially in contrast to multiplex panel codes. Some payers have implemented policies to limit the number of units of 87798 that can be billed to prevent over-reimbursement for what should be a single, bundled panel test. Accurate coding and justification are paramount to ensuring the laboratory receives payment and that the patient does not receive an unexpected bill due to a denied claim.