CPT 87999 Unlisted Microbiology: Reimbursement | OpenPayer

Summary & Overview

CPT 87999: Unlisted Microbiology Procedure

CPT code 87999 is an unlisted microbiology procedure code used to report microbiology tests that lack a specific CPT descriptor. As an unlisted code, 87999 is important nationally because it provides a mechanism for reporting emerging, customized, or otherwise uncategorized microbiology laboratory services that standard codes do not capture. Its use affects laboratory billing workflows, documentation requirements, and payer adjudication processes across major payers. Key payers in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of how 87999 is applied in clinical laboratory settings, typical sites of service, common billing considerations, and the types of benchmarks and policy context relevant to unlisted laboratory codes. The publication outlines payer coverage themes, documentation expectations for unlisted services, and where to look for policy updates or coding guidance. Data not available in the input is noted where applicable, and the content focuses on national implications rather than state-specific rules.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicare87999CPTmicrobiologylaboratoryunlisted procedurebillingmedical codingclinical laboratory

Billing Code Overview

CPT code 87999 is an unlisted microbiology procedure code used to report laboratory microbiology services that do not have a specific CPT code. It captures unique, novel, or otherwise unspecified microbiology tests performed by clinical laboratories.

Service type: Microbiology laboratory procedures
Typical site of service: Clinical laboratory or hospital laboratory setting

Clinical & Coding Specifications

Clinical Context

A 62-year-old hospitalized patient on broad-spectrum antibiotics develops worsening sepsis with persistent fevers and hypotension. Blood cultures remain negative after standard testing but the infectious disease team suspects an unusual or atypical organism (for example, a novel viral pathogen, rare fungus, or emergent bacterial strain) requiring an off‑protocol, laboratory‑developed microbiology assay. A specimen (blood, bronchoalveolar lavage, or tissue) is submitted to the clinical microbiology laboratory for a specialized molecular or biochemical test that has no specific CPT code. The laboratory documents the unique procedure, performs a validated test (such as an in‑house multiplex PCR for an uncommon pathogen, advanced sequencing for pathogen identification, or specialized antigen/antibody assay), and bills using 87999 to report the unlisted microbiology procedure. Typical workflow includes clinician order, specimen accessioning, method validation review by the laboratory director, performance of the procedure by a clinical laboratorian, result verification, and inclusion of interpretive comments in the final report. The service commonly occurs in hospital inpatient laboratories, reference laboratories, academic medical centers, or public health laboratories. For outpatient clinics, emergency departments, and ambulatory surgery centers, 87999 may be used when an off‑protocol or novel microbiology assay is required and no specific CPT exists.

Coding Specifications

Modifier	Description	When to Use

CPT 87906: HIV-1 Genotype by Nucleic Acid (Non-RT/Protease Regions)

CPT-87903-HIV-1-DRUG-RESISTANCE-NUCLEIC-ACID-ANALYSIS

CPT 87903: HIV-1 Drug Resistance Nucleic Acid Analysis

CPT-87905-ENZYMATIC-ACTIVITY-TESTING-INFECTIOUS-AGENT-TECHNICAL

CPT 87905: Enzymatic Activity Testing for Nonviral Infectious Agents

CPT-87900-VIRAL-DRUG-SUSCEPTIBILITY-GENOTYPIC-PHENOTYPE-PREDICTION

CPT 87900: Viral Drug Susceptibility Testing, Genotype-to-Phenotype Prediction

CPT-87904-HIV-1-DRUG-RESISTANCE-ADDITIONAL-DRUG-TESTING

CPT 87904: HIV-1 Drug Resistance Analysis, Additional Drug

CPT-87913-SARS-COV-2-GENOTYPE-ANALYSIS-NEXT-GENERATION-SEQUENCING

CPT 87913: SARS–CoV–2 Genotype Analysis by Next-Generation Sequencing

CPT-87912-HEPATITIS-B-GENOTYPE-ANALYSIS-NUCLEIC-ACID

CPT 87912: Hepatitis B Virus Genotype Analysis, Nucleic Acid

CPT-87910-CMV-GENOTYPE-NUCLEIC-ACID-ANALYSIS

CPT 87910: CMV Genotype Analysis by Nucleic Acid

CPT-87901-HIV-1-GENOTYPE-REVERSE-TRANSCRIPTASE-PROTEASE-ANALYSIS

CPT 87901: HIV-1 Genotype Analysis of Reverse Transcriptase and Protease

CPT-87902-HEPATITIS-C-GENOTYPE-NUCLEIC-ACID-TESTING-TECHNICAL

CPT 87902: Hepatitis C Genotype by Nucleic Acid, Technical Component

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Taxonomy Code	Specialty	Notes
207RH0000X	Infectious Disease	Clinicians who order specialized testing and interpret infectious disease results.
207KP0101X	Clinical Pathology	Pathologists or laboratory directors providing interpretation and oversight of advanced microbiology assays.
207L00000X	Microbiology Laboratory	Clinical laboratory scientists and managers performing the technical testing.
207LP2900X	Public Health Laboratory	Reference and public health laboratory specialists conducting emergent or surveillance testing.
2083P0205X	Critical Care Medicine	Intensivists who commonly order specialized infectious disease testing in ICU settings.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`A41.9`	Sepsis, unspecified organism	Common indication for advanced microbiology testing when cultures are negative or unusual pathogens are suspected.
`R65.21`	Severe sepsis with septic shock	Indicates critically ill patients requiring broad diagnostic testing including unlisted specialized assays.
`J18.9`	Pneumonia, unspecified organism	Respiratory specimens may require atypical testing (molecular, sequencing) reported with `87999`.
`B20`	Human immunodeficiency virus [HIV] disease	Immunocompromised patients often need expanded microbiology testing for opportunistic infections.
`B44.9`	Aspergillosis, unspecified	Fungal infections occasionally require specialized identification methods without specific CPT codes.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`87220`	Culture, bacteria; any source, by fluorescent or chromogenic media, initial isolation (includes identification)	Performed when standard culture methods are applicable; may precede `87999` when initial cultures fail and unlisted molecular testing is needed.
`87471`	Infectious agent detection by nucleic acid (DNA or RNA), direct probe technique, each organism	Used for single-target molecular tests; `87999` may be used when a novel or multi-target assay has no specific code.
`87798`	Infectious agent antigen detection by immunoassay technique, multiple-step, (e.g., enzyme immunoassay), each organism	Used for antigen testing; `87999` applies when an atypical antigen assay lacks a specific CPT.
`87635`	Infectious agent detection by nucleic acid (DNA or RNA); severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), amplified probe technique	Common molecular respiratory pathogen test; `87999` is used for emergent, non‑standard sequencing or novel pathogen assays without specific codes.
`87449`	Infectious agent detection by nucleic acid (DNA or RNA); multiple organisms, any method	Used for multiplex panels with established CPT codes; when an in‑house multiplex panel lacks a code, `87999` may be reported.
`88291`	Microbial identification by nucleic acid (e.g., sequencing), per organism	Used for sequencing-based identification when a specific sequencing code exists; `87999` is used when no specific sequencing CPT applies.

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