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    OpenPayerBilling CodesExamination, Homogenization and Concentration ProceduresCPT cpt-87166-dark-field-microscopy-direct-specimen
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    CPT 87166: Dark-Field Microscopic Exam of Direct Specimen

    CPT code 87166 describes a dark-field microscopic examination of a direct clinical specimen (for example, a smear from a penile lesion) performed by a laboratory analyst; the service type is microscopic diagnostic examination and the typical site of service is a clinical laboratory or pathology/lab department where direct specimen microscopy is performed.

    For related coverage guidance, see recent payer policy updates: Ambulance and Medical Transport Services (Ground, Air and Water) Corporate Medical Policy, Emergency Air/Water Ambulance Services Medical Guideline, Non-Emergent Ambulance Services.

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    Clinical & Coding Specifications

    Clinical Context

    A male patient in his late 20s presents to a sexual health clinic with a painful penile ulcer and purulent discharge after recent unprotected sexual exposure. The clinician performs a focused genital exam and collects a direct specimen from the lesion using a swab and prepares a smear on a glass slide. The slide is sent to the on-site laboratory where a medical technologist performs a microscopic examination on a dark background (dark-field or dark-ground microscopy) to evaluate for motile spirochetes consistent with Treponema pallidum or other organisms. The typical workflow includes specimen collection in clinic, immediate slide preparation, transport to the lab, performance of 87166 dark-field microscopic exam, documentation of findings in the laboratory report, and communication of positive results to the ordering clinician for confirmatory serologic testing and treatment planning. Typical site of service for this procedure is an outpatient clinic, sexually transmitted infection (STI) clinic, or hospital outpatient laboratory where direct microscopy can be performed promptly.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    87177Culture, bacterial; any other source, aerobicPerformed when bacterial culture is indicated in addition to direct microscopy for wound or genital infections.
    87205Smear, Gram or Giemsa, direct smear interpretation by laboratoryPerformed for direct staining of specimens that can complement dark-field microscopy for identification of organisms.
    87070Culture, bacterial; direct probe techniqueMay be used when molecular or probe-based testing is performed alongside microscopic exam for rapid pathogen identification.
    87490Infectious agent antigen detection by immunoassay, chlamydia trachomatisCommonly ordered in STI workups concurrently with dark-field exam to evaluate for co-infection.
    87591Infectious agent detection by nucleic acid (NAA), Treponema pallidumMolecular testing for syphilis can be used to confirm dark-field positive findings (note: specific code availability varies by test).

    Related Modifiers

    6 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…
    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…
    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…

    Related Provider Taxonomies

    8 rows

    Taxonomy Code
    207RC0000X
    207K00000X
    207L00000X
    207RH0000X
    208D00000X
    207VB0002X
    175M00000X
    2085R0202X

    Related Payer Policy Updates

    Specialty: Emergency & Medical Transportation1 / 3

    10 rows

    PolicyPayerEffective Date
    Ambulance and Medical Transport Services (Ground, Air and Water) Corporate Medical Policybcbsvermont2026-10-01
    Emergency Air/Water Ambulance Services Medical GuidelineWPS Health Insurance2026-10-01
    Non-Emergent Ambulance ServicesConnectiCare2026-09-11
    Fixed Wing Air Ambulance TransportCigna2026-08-15
    Air AmbulanceAmbetter Georgia2026-08-01
    Ambulance Services (for New Mexico Only)UnitedHealthcare2026-08-01
    Ambulance Services (for Tennessee Only)UnitedHealthcare2026-08-01
    Clinical Policy: Air AmbulanceAmbetter Nevada2026-08-01
    Air AmbulanceCentene2026-08-01
    Clinical Policy: Air AmbulanceArizona Complete Health2026-08-01

    Related Codes

    CPT-87164-DARK-FIELD-MICROSCOPIC-EXAM-DIRECT-SPECIMEN

    CPT 87164: Dark-Field Microscopy of Direct Specimen

    CPT-87168-ARTHROPOD-IDENTIFICATION-MACROSCOPIC-EXAM

    CPT 87168: Arthropod Identification, Direct Examination

    CPT-87169-PARASITOLOGY-MACROSCOPIC-EXAMINATION

    CPT 87169: Parasite Identification Without Microscope

    CPT-87172-PINWORM-ADHESIVE-TAPE-EXAMINATION

    CPT 87172: Pinworm Examination by Tape or Paddle

    CPT-87176-TISSUE-HOMOGENIZATION-FOR-CULTURE-PREPARATION

    CPT 87176: Tissue Homogenization for Culture Preparation

    CPT-87177-PARASITOLOGY-STOOL-CONCENTRATION-AND-OVA-EVALUATION

    CPT 87177: Stool Parasite and Ova Concentration and Microscopic Evaluation

    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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