2025 CPT code 87184
Effective Date: N/A Pathology and Laboratory Procedures > Microbiology Procedures Feed
Susceptibility studies, antimicrobial agent; disk method, per plate (12 or fewer agents)
Modifiers 59 and 91 are applicable as described in the coding guidelines. Other modifiers may be applicable depending on the specific circumstances.
Medical necessity for this test is established when a patient has a suspected bacterial infection, and knowledge of the causative organism's antibiotic susceptibility is essential for guiding appropriate therapy.
Following the culture, isolation, and identification of a microorganism, a fresh agar plate is inoculated with the isolate. Up to 12 disks, each containing a different antimicrobial agent, are placed on the agar. The plate is incubated, and the zones of inhibition are measured to determine the organism's susceptibility to each agent.
In simple words: This test helps doctors choose the right antibiotic for an infection. A sample of the bacteria causing the infection is spread on a special gel. Small discs containing different antibiotics are placed on the gel.The antibiotic spreads into the gel. If the bacteria can't grow near a disc, it means that antibiotic might work against the infection.
This procedure involves evaluating a culture isolate's susceptibility to up to 12 antimicrobial agents using the disk diffusion method (Kirby-Bauer method).A standard concentration of the isolated organism is swabbed onto an agar plate. Disks containing different antimicrobial agents are placed on the agar. After incubation, the zones of inhibition are measured to determine susceptibility.
Example 1: A patient presents with a suspected urinary tract infection (UTI). A urine culture is performed, and Escherichia coli is isolated. Antimicrobial susceptibility testing (AST) using the disk diffusion method is performed to determine which antibiotics are most effective against the isolated E. coli, guiding treatment decisions., A patient with a wound infection grows Staphylococcus aureus. AST by disk diffusion is performed to identify the appropriate antibiotic for treatment, considering potential methicillin resistance., A patient with pneumonia has a sputum sample culture that grows Streptococcus pneumoniae. To guide appropriate antibiotic therapy, AST using the disk diffusion method is performed to determine the bacteria's susceptibility to various antibiotics commonly used to treat pneumonia.
Documentation should include the organism isolated, the method used for susceptibility testing (disk diffusion), the antibiotics tested, the measured zone of inhibition for each antibiotic, and the interpretation of the results (susceptible, intermediate, or resistant). The clinical indication for the test should also be documented.
- Revenue Code: T1H - LAB TESTS - OTHER (NON-MEDICARE FEE SCHEDULE)
- Specialties:Microbiology, Infectious Disease
- Place of Service:Independent Laboratory, Hospital Laboratory