Summary & Overview
CPT 87184: Antimicrobial Susceptibility Testing by Disk Diffusion
CPT code 87184 represents a standard microbiology laboratory procedure that tests a culture isolate’s susceptibility to up to 12 antimicrobial agents using disk diffusion. This assay is a core diagnostic tool for guiding antimicrobial therapy and tracking resistance patterns at a population level, making it clinically and operationally important for hospitals, outpatient clinics, public health laboratories, and reference labs across the country. Key payers addressed in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare.
Readers will find a concise explanation of the code’s clinical purpose, typical sites of service, and how the procedure fits into laboratory workflows. The publication provides benchmarks and billing guidance context where available, highlights common payer coverage considerations, and summarizes relevant policy updates affecting laboratory reimbursement and coding practice. Clinical context includes the role of disk diffusion susceptibility testing in informing antibiotic selection and antimicrobial stewardship programs. For fields not provided in the source input, such as associated taxonomies and specific ICD-10 pairings, the summary notes that those details are not available in the input. This national-level overview is intended for billing managers, laboratory directors, and policy analysts seeking a practical briefing on CPT code 87184.
Billing Code Overview
CPT code 87184 describes a laboratory procedure in which a technologist or lab analyst evaluates a culture isolate’s antimicrobial susceptibility to up to 12 specific agents by placing impregnated disks on an agar plate inoculated with the isolate. The test assesses whether a microorganism is sensitive, intermediate, or resistant to the tested antibiotics based on zones of inhibition around the disks.
Service type: Microbiology laboratory antimicrobial susceptibility testing (disk diffusion method)
Typical site of service: Clinical or hospital microbiology laboratory, outpatient laboratory, or reference laboratory
Data not available in the input.
Clinical & Coding Specifications
Clinical Context
A 62-year-old male is admitted to the hospital with fever, dysuria, and flank pain. Urine culture grows a Gram-negative bacillus; the microbiology laboratory performs antimicrobial susceptibility testing by disk diffusion to determine which antibiotics are effective. A laboratory technologist inoculates Mueller-Hinton agar with the isolate, places up to 12 antibiotic-impregnated disks on the plate, incubates, and measures zones of inhibition to report susceptibility results. Results guide the inpatient team’s antibiotic selection and may trigger an infection control consult if a multidrug-resistant organism is identified. Typical site of service is a hospital clinical microbiology laboratory or a freestanding diagnostic laboratory performing bacteriology and susceptibility testing. The service type is a microbiology laboratory technical procedure (antimicrobial susceptibility testing, disk diffusion) billed by the performing laboratory or hospital under the laboratory fee schedule.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when reporting the physician professional interpretation separate from the technical lab performance (rare for this test). |
59 | Distinct procedural service |