87505

Infectious agent detection by nucleic acid (DNA or RNA); Clostridioides difficile (e.g., C. difficile) toxin gene(s), amplified probe technique, each strain

This CPT code describes a molecular diagnostic test employed to detect the presence of *Clostridioides difficile* (formerly *Clostridium difficile*) toxin gene(s) in a clinical specimen, most commonly stool. The procedure involves a nucleic acid amplification technique (NAAT), such as polymerase chain reaction (PCR), coupled with probe detection. This test specifically identifies the genetic material (DNA or RNA) encoding for *C. difficile* toxins (e.g., tcdA and/or tcdB), which are directly implicated in the pathogenesis of *Clostridioides difficile* infection (CDI) and its associated symptoms, including pseudomembranous colitis and severe diarrhea. This method offers high sensitivity and specificity for the direct detection of toxigenic *C. difficile*.

Clinical Indications

  • Diagnosis of *Clostridioides difficile* infection (CDI) in patients presenting with new onset or worsening diarrhea (typically three or more unformed stools in 24 hours), especially following antibiotic use or hospitalization.
  • Evaluation of suspected recurrent CDI in patients with a history of prior *C. difficile* infection and symptom recurrence.
  • Differentiation between *C. difficile* colonization and active infection when clinical presentation, risk factors, and other diagnostic criteria are considered.
  • Investigation and control of *Clostridioides difficile* outbreaks within healthcare facilities or communal living settings.

Procedure Steps

  1. **Specimen Collection**: Collection of an appropriate clinical specimen, typically an unformed stool sample from the patient. Rectal swabs may be used in specific circumstances.
  2. **Nucleic Acid Extraction**: Isolation and purification of DNA or RNA from the collected specimen to separate the target genetic material of *Clostridioides difficile* from other cellular components.
  3. **Amplification**: The extracted nucleic acids are subjected to a nucleic acid amplification technique (NAAT), commonly polymerase chain reaction (PCR), to exponentially increase the number of copies of specific *C. difficile* toxin gene sequences (e.g., tcdA, tcdB).
  4. **Detection with Probes**: The amplified DNA/RNA fragments are then detected using specific fluorescent or labeled probes that bind exclusively to the target gene sequences.
  5. **Analysis and Interpretation**: The presence or absence of the target toxin gene(s) is analyzed by specialized equipment, and the results are interpreted to determine if toxigenic *C. difficile* is present in the specimen.

Coding Guidelines

  • CPT code 87505 is used for the detection of *Clostridioides difficile* toxin gene(s) using an amplified probe technique.
  • This code is generally reported once per patient encounter for a single diagnostic test, irrespective of how many specific toxin genes (e.g., tcdA, tcdB) are detected within that single test, as the descriptor specifies 'toxin gene(s)'. The phrase 'each strain' primarily refers to the detection of the toxin gene(s) associated with *C. difficile*, not necessarily multiple, distinct toxigenic strains within a single sample for routine clinical purposes.
  • Do not report 87505 in conjunction with other *C. difficile* diagnostic tests (e.g., enzyme immunoassays for *C. difficile* toxin A/B, glutamate dehydrogenase (GDH) antigen tests, or culture methods) when the molecular amplified probe technique is utilized as the primary diagnostic method for the same patient encounter.
  • Comprehensive documentation must be maintained in the patient's medical record to support the medical necessity of performing this test, including clinical symptoms (e.g., diarrhea), relevant risk factors (e.g., recent antibiotic use, hospitalization), and a clear clinical suspicion of *Clostridioides difficile* infection.

Associated ICD-10 Codes