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    v1.0.30
    OpenPayerBilling CodesAntimicrobial Susceptibility StudiesCPT cpt-87187-mlc-antimicrobial-susceptibility-testing
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    CPT 87187: Minimum Lethal Concentration (Antimicrobial Susceptibility)

    CPT code 87187 represents laboratory work where a clinical microbiology technologist or lab analyst performs the technical procedures to determine the minimum lethal concentration (MLC) of an antimicrobial agent for a specific culture isolate; this is an antimicrobial susceptibility test performed as a clinical laboratory service typically provided in a hospital or clinical microbiology laboratory (inpatient or outpatient laboratory settings).

    For related coverage guidance, see recent payer policy updates: Biomarker Testing for Autoimmune Rheumatic Disease, Immunopharmacologic Monitoring of Therapeutic Serum Antibodies, Immune Cell Function Assay.

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    Clinical & Coding Specifications

    Clinical Context

    A 68-year-old inpatient with a recent hospitalization for community-acquired pneumonia has a persistent febrile illness and blood cultures that grew a non‑susceptible Gram‑negative organism. The clinical microbiology laboratory isolates the organism and the laboratorian performs antimicrobial susceptibility testing with determination of the minimum lethal concentration (MLC) for one or more antimicrobial agents to guide therapy. Specimen processing occurs in the hospital microbiology laboratory (typical site of service: hospital clinical laboratory or independent diagnostic laboratory). The workflow includes isolate identification (culture), preparation of standardized inoculum, exposure to serial dilutions of the antimicrobial agent, incubation, and assessment of the lowest concentration that results in bacterial death (MLC), with documentation in the laboratory information system and communication of results to the treating infectious disease clinician and antimicrobial stewardship program.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    87070Culture, bacterial, any source, isolated colony, for identification and antimicrobial susceptibility, with isolation and colony selectionPerformed before 87187; culture and isolation of the organism are prerequisites for MLC testing.
    87077Antimicrobial susceptibility; single commercially prepared disk or tabletAlternative or adjunct method for susceptibility testing—often used for preliminary guidance prior to MLC determination.
    87186Microbial identification by any method; organism identification, bacterial, direct probe, or other rapid methodsIdentification of the isolate may be performed prior to or concurrent with susceptibility testing to guide selection of antimicrobials for MLC testing.
    87188Antimicrobial susceptibility testing, qualitative or quantitative, other methods (e.g., E test)Related susceptibility methods that may be performed instead of or in addition to an MLC determination; part of the overall susceptibility testing workflow.
    87210Smear, primary source with interpretation, for infectious agentInitial microscopic examination that may accompany culture workflows leading to susceptibility testing.

    Related Modifiers

    8 rows

    ModifierDescriptionWhen to Use
    26Modifier 26 (Professional Component) identifies and bills only the professional portion of a split service — the physician’s interpretation, report, and medical judgment — when the technical…- Use CPT Modifier -26 when you are billing only the professional component (PC) of a split‑bill eligible service—i.e., you performed the physician interpretation, medical judgment and prepared a…
    90Modifier ‑90 (Reference/Outside Laboratory) indicates that a laboratory test was performed by an entity other than the treating or reporting provider. The American Medical Association defines…- Use CPT modifier -90 when a laboratory test is performed by an outside/reference laboratory (an entity other than the treating or reporting physician or qualified professional) and the claim needs…
    91Modifier 91 — “Repeat Clinical Diagnostic Laboratory Test” — is appended when the exact same CPT laboratory test is performed more than once for the same patient on the same day because serial,…- Use modifier 91 when the exact same CPT laboratory test is performed more than once on the same patient on the same date because serial or repeated testing is medically necessary to monitor…
    52Modifier ‑52 (Reduced Services) indicates that a service or procedure was partially reduced or omitted at the provider’s discretion, allowing reporting of the basic procedure number with a qualifier…- Use modifier -52 when a physician or qualified health professional electively reduces or omits part of a procedure or service (for example, performing fewer required views or omitting a portion of…
    59Modifier 59 indicates a distinct procedural service when two procedures that are not normally billed together are clinically and procedurally separate. The CPT definition (as reiterated by CMS)…- Use modifier -59 to report a distinct procedural service when documentation supports that the procedure reported is not normally billed together with another service on the same day because of a…
    78CPT modifier -78 indicates an unplanned, related return to the operating or procedure room by the same provider during the global postoperative period. It is appended when treatment for a…- Use modifier -78 when an unplanned, related complication during the original procedure’s global postoperative period requires the patient to return to a formal operating or procedure room and the…
    80CPT® Modifier 80 (Assistant Surgeon) is appended to a surgical CPT code when a physician (MD or DO) provides full, continuous assistance throughout the operative procedure. It is intended only for…- Use CPT Modifier -80 when a physician (MD or DO) serves as an assistant surgeon and provides full, continuous assistance throughout the entire operative procedure; append -80 to the surgical CPT…
    82Modifier 82 is appended to a surgical CPT code to indicate that an attending physician acted as an assistant because a qualified resident surgeon was unavailable. In teaching hospitals it documents…- When to use: Append modifier 82 in teaching-hospital settings to indicate a physician served as an assistant surgeon because a qualified resident surgeon was unavailable (includes situations where…

    Related Provider Taxonomies

    8 rows

    Taxonomy Code
    175F00000X
    282NR1301X
    2080A0000X
    103T00000X
    2080T0004X
    207RN0300X
    207Q00000X
    163WG0100X

    Related ICD-10-CM Codes

    25 rows

    ICD-10-CM CodeDescription
    A23.9Brucellosis, unspecified
    A30.9Leprosy, unspecified
    A41.9Sepsis, unspecified organism
    A42.9Actinomycosis, unspecified
    A49.1Streptococcal infection, unspecified site
    A49.9Bacterial infection, unspecified
    A54.89Other gonococcal infections
    A56.09Other chlamydial infection of lower genitourinary tract
    B95.3Streptococcus pneumoniae as the cause of diseases classified elsewhere
    B96.89Other specified bacterial agents as the cause of diseases classified elsewhere

    Showing 1–10 of 25

    Related Payer Policy Updates

    Specialty: Immunology/Rheumatology1 / 3

    10 rows

    PolicyPayerEffective Date
    Biomarker Testing for Autoimmune Rheumatic DiseaseOscar Health2026-10-01
    Immunopharmacologic Monitoring of Therapeutic Serum AntibodiesOscar Health2026-10-01
    Immune Cell Function AssayOscar Health2026-10-01
    Biomarker Testing for Autoimmune Rheumatic DiseaseBlue Cross Blue Shield - New Mexico2026-09-04
    Inflammatory Conditions - Orencia Intravenous Preferred Specialty Management Policy for Legacy Prescription Drug ListsCigna2026-09-01
    Secukinumab (Cosentyx) — intravenous (Medicare Advantage)blue cross blue shield - louisiana2026-09-01
    Intravenous Immune Globulin (IVIG) — indications and authorization criteriaBlue Cross Blue Shield - Iowa2026-08-28
    Infliximab Intravenous Products Preferred Specialty Management PolicyCigna2026-08-15
    Kineret (anakinra) — Coverage CriteriaBlue Cross Blue Shield - Iowa2026-08-14
    Actimmune (interferon gamma-1b) — Prior Authorization and Coverage Criteriameridian_health_plan_of_michigan2026-08-01

    Related Codes

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

    CPT 87181: Antimicrobial Susceptibility Test, Gradient Diffusion

    CPT-87182-MULTIPLEX-CARBAPENEMASE-IMMUNOASSAY

    CPT 87182: Multiplex Carbapenemase Immunoassay

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

    CPT 87183: Detection of Carbapenem Resistance Genes, Per Isolate

    CPT-87184-ANTIMICROBIAL-SUSCEPTIBILITY-DISK-DIFFUSION

    CPT 87184: Antimicrobial Susceptibility by Disk Diffusion (up to 12 agents)

    CPT-87185-ANTIMICROBIAL-ENZYME-DETECTION-SUSCEPTIBILITY-TEST

    CPT 87185: Antimicrobial Susceptibility Enzyme Detection

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

    CPT 87186: Antimicrobial Susceptibility Testing by Dilution Methods

    CPT-87188-ANTIMICROBIAL-SUSCEPTIBILITY-MACROBROTH-DILUTION

    CPT 87188: Macrobroth Dilution Antimicrobial Susceptibility Test

    CPT-87190-MYCOBACTERIA-PROPORTION-METHOD-SUSCEPTIBILITY-TESTING

    CPT 87190: Mycobacteria Susceptibility Testing, Proportion Method

    CPT-87197-BACTERIAL-TITER-ANTIBIOTIC-SUSCEPTIBILITY

    CPT 87197: Bacterial Titer for Antibiotic Susceptibility

    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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