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    v1.0.30
    OpenPayerBilling CodesAntimicrobial Susceptibility StudiesCPT cpt-87188-antimicrobial-susceptibility-macrobroth-dilution
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    CPT 87188: Macrobroth Dilution Antimicrobial Susceptibility Test

    CPT code 87188 describes a laboratory macrobroth dilution antimicrobial susceptibility test in which a lab analyst performs the technical procedures to evaluate a culture isolate’s sensitivity to multiple antimicrobial agents by observing growth of the isolate in varying concentrations; service type: clinical microbiology laboratory procedure; typical site of service: clinical microbiology lab / hospital laboratory or reference lab.

    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 hospitalized adult with suspected bloodstream infection has a positive blood culture that grows a bacterial isolate. The microbiology laboratory receives the isolate and performs identification and antimicrobial susceptibility testing by macrobroth dilution to determine minimum inhibitory concentrations for multiple antibiotics. The workflow: clinical team submits blood cultures; on growth, lab technologist isolates organism on media and performs identification (e.g., MALDI-TOF or biochemical methods). A laboratory analyst then performs the technical macrobroth dilution steps, incubates isolates in graded antibiotic concentrations, reads growth endpoints, and reports susceptibility results to the clinical team to guide targeted antimicrobial therapy. Typical site of service is the hospital microbiology laboratory or independent clinical laboratory supporting inpatient and outpatient facilities. The patient scenario often involves sepsis, bacteremia, complicated urinary tract infection, pneumonia, or postoperative wound infection where targeted therapy depends on susceptibility patterns. Turnaround time is generally 24–72 hours after isolate recovery depending on organism and test complexity.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    87070Culture, any other source, bacterial; screening only, pathogenic organisms not isolatedPerformed when initial culture is set up to detect growth prior to isolate workup; may precede susceptibility testing.
    87140Culture, bacterial; isolation and presumptive identificationPerformed to isolate and presumptively identify organism before susceptibility testing like macrobroth dilution.
    87186Susceptibility studies, other methods, by MIC, e.g., microbroth dilution; single isolate, each antimicrobial agentAlternative susceptibility testing methodology (microbroth dilution) often performed alongside or instead of macrobroth dilution.
    87210Smear, primary source with interpretation; Gram or Giemsa stainRapid microscopy performed on clinical specimens to guide initial therapy prior to culture and susceptibility results.
    87491Infectious agent detection by nucleic acid (DNA or RNA); Chlamydia trachomatis, amplified probe technique, eachMolecular identification tests that may accompany culture workup for rapid organism identification (example of tests commonly ordered in parallel).

    Related Modifiers

    9 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…
    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…
    76Modifier -76, Repeat Procedure or Service by Same Physician or Other Qualified Health Care Professional, is appended when the same provider performs an identical, medically necessary procedure or…- Use modifier -76 when the same physician or other qualified health care professional performs an identical procedure or service a second (or subsequent) time on the same date of service and the…
    77Modifier 77 indicates that a previously performed procedure or service was legitimately repeated by a different physician or other qualified health care professional. The AMA’s CPT definition…- Use modifier 77 when a basic procedure or service already performed is repeated by a different physician or other qualified health care professional (for example, a second provider independently…
    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…
    53Modifier 53 (Discontinued Procedure) signals that a surgical or diagnostic service was begun by the physician but terminated because of extenuating circumstances that threatened the patient’s…- Use modifier -53 when a physician/qualified healthcare professional has started a surgical or diagnostic procedure (e.g., anesthesia administered, incision or scope insertion) and then discontinues…
    22Modifier –22 (Increased Procedural Services) is used when a reported procedure is substantially more extensive than normally required. The CPT Manual and CMS state it may be appended only when the…- When to use: Append modifier -22 to a procedural CPT code when the service performed is substantially more extensive than the usual service described by that code — i.e., the procedure required…

    Related Provider Taxonomies

    8 rows

    Taxonomy Code
    207P00000X
    363L00000X
    363LF0000X
    163WM0705X
    111NP0017X
    207YP0228X
    251B00000X
    364SH1100X

    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-87187-MLC-ANTIMICROBIAL-SUSCEPTIBILITY-TESTING

    CPT 87187: Minimum Lethal Concentration (Antimicrobial Susceptibility)

    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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