CPT 87185 Reimbursement & Policy | OpenPayer

Summary & Overview

CPT 87185: Enzyme Detection for Antimicrobial Susceptibility Testing

CPT code 87185 denotes a laboratory technical procedure to evaluate a cultured organism’s susceptibility to antimicrobial agents by detecting enzyme production (for example, beta-lactamase) that can render certain antibiotics ineffective. This molecular/biochemical susceptibility test is central to guiding targeted antimicrobial therapy, supporting antimicrobial stewardship, and informing infection control practices across inpatient and outpatient settings. Nationally, accurate reporting of such diagnostic codes affects laboratory billing, public health surveillance, and clinical decision support.

Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find context on clinical purpose and typical sites of service, an outline of what this code represents for laboratory workflows, and direction on where to find additional billing and policy guidance. The publication addresses benchmark considerations and policy updates relevant to laboratory reimbursement and documentation practices, and clarifies the clinical role of enzyme-detection susceptibility testing in informing antibiotic selection.

The report is intended for laboratory managers, billing professionals, hospital administrators, and clinicians who need a concise reference to the clinical meaning and billing context of CPT code 87185 for national practice settings. Data not available in the input are noted where applicable.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicare87185CPTmicrobiologyantimicrobial-susceptibilitybeta-lactamaselaboratory-testingclinical-labinfectious-diseaseantimicrobial-stewardship

Billing Code Overview

CPT code 87185 describes a laboratory procedure in which a lab analyst performs the technical steps to evaluate a culture isolate’s susceptibility to antimicrobial agents by detecting organism production of a specific enzyme (for example, beta-lactamase) that interferes with certain antibiotics. This is a microbiology susceptibility or resistance test focused on enzyme-mediated antibiotic interference.

Service type: Laboratory diagnostic susceptibility testing (technical component)
Typical site of service: Clinical microbiology laboratory or hospital laboratory performing culture-based antimicrobial susceptibility testing

Data not available in the input for payers, associated taxonomies, ICD-10 diagnoses, and related codes.

Clinical & Coding Specifications

Clinical Context

A 68-year-old male nursing home resident presents with fever, productive cough, and worsening shortness of breath. A sputum specimen is collected and sent to the microbiology laboratory. A respiratory bacterial culture grows a Gram-negative bacillus suspected to be Haemophilus influenzae. The laboratory performs organism identification followed by antimicrobial susceptibility testing focused on detection of beta-lactamase production to determine whether penicillins or certain cephalosporins will be effective. A trained laboratory technologist or clinical microbiologist carries out the technical steps of the enzymatic assay on the culture isolate, documents results in the laboratory information system, and reports findings to the ordering clinician to guide antibiotic selection.

Typical workflow steps:

Receive and accession patient specimen in the microbiology lab.
Isolate organism on culture media and confirm colony morphology and identification tests.
Perform beta-lactamase or other enzyme-based susceptibility assay (technical component).
Record and verify results; include interpretive category (susceptible, intermediate, resistant) in the report.
Transmit results to the ordering provider and enter into the patient record for antimicrobial stewardship and treatment decisions.

Coding Specifications

Modifier	Description

CPT 87190: Mycobacteria Susceptibility Testing, Proportion Method

CPT-87186-ANTIMICROBIAL-SUSCEPTIBILITY-TESTING-DILUTION-METHODS

CPT 87186: Antimicrobial Susceptibility Testing by Dilution Methods

CPT-87188-ANTIMICROBIAL-SUSCEPTIBILITY-MACROBROTH-DILUTION

CPT 87188: Antimicrobial Susceptibility Testing by Macrobroth Dilution

CPT-87181-ANTIMICROBIAL-SUSCEPTIBILITY-GRADIENT-DIFFUSION-TEST

CPT 87181: Antimicrobial Susceptibility Testing, Gradient Diffusion

CPT-87184-ANTIMICROBIAL-SUSCEPTIBILITY-DISK-DIFFUSION

CPT 87184: Antimicrobial Susceptibility Testing by Disk Diffusion

CPT-87197-BACTERIAL-TITER-ANTIBIOTIC-SUSCEPTIBILITY

CPT 87197: Bacterial Titer for Antibiotic Susceptibility

CPT-87182-MULTIPLEX-CARBAPENEMASE-IMMUNOASSAY

CPT 87182: Multiplex Immunoassay for Carbapenemase Detection

CPT-87183-CARBAPENEM-RESISTANCE-GENE-DETECTION-PER-ISOLATE

CPT 87183: Detection of Carbapenem Resistance Genes, Per Isolate

CPT-87187-MLC-ANTIMICROBIAL-SUSCEPTIBILITY-TESTING

CPT 87187: Minimum Lethal Concentration (MLC) Antimicrobial Testing

Taxonomy Code	Specialty	Notes
0000A0400X	Clinical Laboratory Scientist	Performs technical microbiology testing and susceptibility assays.
207R00000X	Infectious Disease Specialist	Interprets susceptibility results for antimicrobial management.
207L00000X	Clinical Pathologist	Oversees laboratory testing, quality control, and result validation.
363L00000X	Microbiologist	Directly involved in organism identification and enzymatic assays.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`J15.9`	Unspecified bacterial pneumonia	Culture and beta-lactamase testing guide antibiotic selection when bacterial pneumonia is suspected.
`J18.9`	Pneumonia, unspecified organism	Used when organism is not yet identified; susceptibility testing informs definitive therapy.
`A49.9`	Bacterial infection, unspecified	Broad code for bacterial infections where isolate susceptibility testing is required.
`J22`	Unspecified acute lower respiratory infection	Empiric therapy adjusted based on lab enzyme-based susceptibility results.
`N39.0`	Urinary tract infection, site not specified	Bacterial isolates from urine may require beta-lactamase testing to determine oral antibiotic choices.
`L03.90`	Cellulitis, unspecified	Wound or skin culture isolates undergo susceptibility testing including enzyme detection to guide therapy.
`A41.9`	Sepsis, unspecified organism	Rapid detection of resistance mechanisms can have major impact on targeted antimicrobial therapy in systemic infection.
`B96.89`	Other specified bacterial agents as the cause of diseases classified elsewhere	Used to identify specific bacterial pathogens found by culture and susceptibility testing.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`87070`	Culture, bacterial, aerobic with isolation and presumptive identification	Often performed prior to susceptibility testing to isolate and presumptively identify the organism that will undergo enzyme-based testing.
`87077`	Culture, fungal, other and culture with isolation and presumptive identification	Performed when fungal pathogens are a consideration; not routine for bacterial beta-lactamase testing but part of comprehensive workup when indicated.
`87186`	Susceptibility testing; disk diffusion (e.g., Kirby-Bauer), antimicrobial agents	Alternative or complementary susceptibility method to enzyme detection; may be performed alongside enzymatic testing to provide broader susceptibility data.
`87205`	Smear, primary source with interpretation by physician; Gram or Giemsa stain	Rapid diagnostic adjunct used to guide initial organism identification before culture and susceptibility testing.
`87880`	Infectious agent detection by nucleic acid (DNA or RNA), direct probe; qualitative, multiple organisms	Molecular methods that may detect resistance genes (e.g., beta-lactamase genes) and can complement phenotypic enzyme assays.

`26`	Professional component	When a physician provides the professional interpretation or consultative input for the test results separate from technical processing.
`TC`	Technical component	To report only the laboratory technical work when the performing lab bills for the testing procedures.
`59`	Distinct procedural service	When this test is a distinct service from other procedures performed the same day (careful use required).
`90`	Reference (outside) laboratory	When the specimen is sent to an independent reference lab that performs the testing.
`91`	Repeat clinical diagnostic laboratory test	When the same assay is repeated on the same day for verification or quality control purposes.
`QK`	CLIA waived test performed by laboratory personnel under direct supervision	When applicable in specific waived testing contexts (facility-specific rules apply).
`QX`	Rendering provider CLIA certified	When the performing individual is CLIA-certified to perform the laboratory testing.
`QY`	Laboratory test performed in whole or in part by a physician office laboratory	When the test was performed in a physician office laboratory setting.
`52`	Reduced services	When the full procedure was partially reduced or not completed as typically described.
`53`	Discontinued procedure	If testing was started but discontinued for documented clinical reasons.
`59`	Distinct procedural service	When documentation supports this assay as separate from other lab services billed the same date.
`78`	Unplanned return to OR by same physician	Not typically applicable; included from list but rarely used for lab procedures.
`82`	Assistant not available	Not typically applicable to lab technical work; rarely used.
`91`	Repeat clinical diagnostic laboratory test	When a confirmatory repeat test is performed to validate results.

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