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Infectious agent antigen detection by immunoassay with direct optical observation; Clostridium difficile toxin A

CPT4 code

Name of the Procedure:

Infectious agent antigen detection by immunoassay with direct optical observation; Clostridium difficile toxin A (C. difficile toxin A test).


The C. difficile toxin A test is used to detect the presence of toxin A produced by the Clostridium difficile bacteria in a stool sample. This test helps diagnose infections caused by C. difficile, which can lead to severe diarrhea and other intestinal issues.


The C. difficile toxin A test is primarily used to diagnose an infection caused by Clostridium difficile. This bacterium is responsible for causing significant gastrointestinal problems, especially after the use of antibiotics. The goal is to identify the presence of toxin A, facilitating appropriate treatment to prevent complications.


  • Persistent diarrhea
  • Abdominal pain and cramping
  • Fever and nausea
  • Recent antibiotic use
  • Suspected C. difficile infection in a patient with a weakened immune system


  • No specific fasting or medication adjustments are typically required.
  • Patients may be asked to provide a fresh stool sample for the test.

Procedure Description

  1. Collection of a stool sample from the patient.
  2. The sample is treated and placed onto a test device containing antibodies specific to C. difficile toxin A.
  3. As the sample moves through the device, if toxin A is present, it binds to the antibodies, creating a visible signal observed by the technician.
  4. Results are interpreted based on the appearance of the signal (usually a color change).


  • Test device with specific antibodies
  • Stool sample container

No anesthesia or sedation is needed for this procedure.


The actual test procedure takes approximately 1-2 hours, but results may be available within a few hours to a day, depending on the laboratory's workload.


This test is typically performed in a hospital laboratory or an outpatient clinic equipped with the necessary testing facilities.


  • Medical laboratory technicians or technologists
  • Microbiologists (for result interpretation)

Risks and Complications

  • Minimal risks associated with the procedure itself, as it involves only stool sample collection.
  • Rare possibility of false-positive or false-negative results, which may lead to misdiagnosis or delayed treatment.


  • Accurate diagnosis of C. difficile infection
  • Provides timely information for effective treatment
  • Helps prevent the spread of infection and potential complications


  • No recovery time needed since it is a non-invasive test.
  • Patients can resume normal activities immediately after providing the stool sample.


  • Polymerase chain reaction (PCR) testing for C. difficile toxin genes
  • Enzyme immunoassay (EIA) for both toxins A and B
  • Cell cytotoxicity assay

Pros and Cons:

  • PCR is more sensitive but also more expensive and requires specialized equipment.
  • EIA can detect both toxins but may have lower sensitivity.
  • Cell cytotoxicity assay is highly sensitive but time-consuming and technically demanding.

Patient Experience

  • The patient may feel discomfort or embarrassment during the stool sample collection process.
  • The procedure itself is painless and straightforward.
  • Comfort measures include private collection facilities and clear instructions to ensure ease during the sample collection process. Pain management is not necessary for this non-invasive test.

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