Summary & Overview

CPT 86645: Cytomegalovirus (CMV) IgM Antibody Immunoassay

CPT code 86645 denotes a laboratory immunoassay performed to detect Cytomegalovirus (CMV) immunoglobulin M (IgM) antibodies, a marker of recent or acute CMV infection. This code is nationally relevant because CMV testing informs diagnosis and management across obstetrics, transplant care, neonatology, and immunocompromised populations. Accurate coding supports clinical decision-making, public health surveillance, and appropriate laboratory reimbursement.

Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of what the code represents, typical sites of service, and the clinical context for ordering CMV IgM testing. The publication outlines common billing considerations and related benchmarks where available. It also summarizes payer coverage patterns and any policy-relevant updates when present.

The report is intended to help billing professionals, laboratory managers, and clinicians understand the clinical purpose of the test, the service setting, and the types of payers who commonly cover this service. Data not available in the input are noted where applicable.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicareCPT 86645CMV IgMlaboratoryimmunoassayinfectious disease testingclinical labdiagnostic testingserology

Billing Code Overview

CPT code 86645 describes an immunoassay for detection of Cytomegalovirus (CMV) immunoglobulin M (IgM) antibodies in a patient’s blood. This test evaluates recent or acute CMV infection by identifying the presence of IgM-class antibodies directed against CMV.

Service type: Laboratory diagnostic immunoassay

Typical site of service: Clinical laboratory or hospital laboratory

Clinical & Coding Specifications

Clinical Context

A 28-year-old pregnant woman presents to the obstetrics clinic at 10 weeks' gestation with a history of recent febrile illness and flu-like symptoms and concerns about possible exposure to Cytomegalovirus (CMV) from a toddler in daycare. The obstetrician orders a maternal serologic panel including CMV IgM to evaluate for recent primary CMV infection, which can have implications for fetal risk. Venipuncture is performed in the outpatient lab; a serum specimen is processed and routed to the clinical immunology lab. The laboratory analyst performs an immunoassay to detect CMV-specific immunoglobulin M (IgM) antibodies using a validated automated platform. Results are reported in the electronic medical record and communicated to the ordering obstetrician. If the result is positive or equivocal, reflex testing for CMV IgG and IgG avidity or polymerase chain reaction (PCR) testing of maternal blood or amniotic fluid may be ordered to further determine timing and significance of infection. Typical sites of service include outpatient physician offices, hospital outpatient laboratories, and independent clinical diagnostic laboratories. This test is commonly billed for pregnant patients, neonates with suspected congenital infection, and immunocompromised adults with signs of acute CMV disease.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the professional interpretation component if the laboratory testing has a separate technical component billed by the performing lab.
`TC`	Technical component	Use when billing only the technical component for the laboratory equipment, reagents, and technical staff.
`91`	Repeat clinical diagnostic laboratory test	Use when repeating the same `86645` test on the same day to obtain a subsequent measurement for accuracy or monitoring.
`90`	Reference (outside) laboratory	Use when the test is performed by an outside reference laboratory and results are reported by the billing provider.
`59`	Distinct procedural service	Use when `86645` is billed the same day as another procedure and the services are distinct and separate from other tests or encounters.
`52`	Reduced services	Use when the service performed was partially reduced or not completed as described by the full CPT code.
`53`	Discontinued procedure	Use when the testing procedure was started but discontinued due to patient factors or specimen issues.
`78`	Unplanned return to the operating/procedure room by the same physician following initial procedure for a related procedure during the postoperative period	Rare for this code but applicable if a procedure-related complication necessitates return and the laboratory testing is associated with that event.
`90`	Reference (outside) laboratory	Use when the specimen is sent to an outside lab for testing and only the referring lab bills for coordinating services.
`91`	Repeat clinical diagnostic laboratory test	Use for repeat testing to confirm unexpected or critical values.

Taxonomy Code	Specialty	Notes
`208W00000X`	Clinical Laboratory Technician	Performs specimen handling and assay execution in the lab.
`2080P0002X`	Clinical Pathology	Pathologists or clinical laboratory directors who oversee testing and result interpretation.
`207K00000X`	Obstetrics & Gynecology	Ordering clinicians who request CMV IgM in pregnant patients.
`207L00000X`	Pediatrics	Providers ordering CMV testing for neonates and infants with suspected congenital infection.
`2081S0122X`	Infectious Disease	Specialists who manage suspected acute CMV disease in immunocompromised patients.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`O98.511`	Viral disease in pregnancy, cytomegaloviral disease in pregnancy	Direct indication for maternal CMV testing with `86645` to assess recent infection and fetal risk.
`P35.1`	Congenital cytomegalovirus infection	Relevant when testing neonates or infants where congenital CMV is suspected.
`B25.9`	Cytomegaloviral disease, unspecified	Used for symptomatic CMV disease in adults or immunocompromised patients prompting CMV IgM testing.
`Z20.821`	Contact with and (suspected) exposure to cytomegalovirus	Used when testing is performed due to known exposure history.
`R50.9`	Fever, unspecified	Nonspecific indication prompting infectious workup including CMV IgM in appropriate clinical contexts.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`36415`	Collection of venous blood by venipuncture	Performed immediately prior to `86645` to obtain the serum specimen for CMV IgM testing.
`86644`	Cytomegalovirus (CMV) antibody, IgG, immunoassay	Commonly ordered alongside `86645` to determine immune status (IgG) and help interpret IgM results for acute versus past infection.
`86641`	Epstein-Barr virus (EBV) antibody, IgM, immunoassay	May be ordered in differential evaluation of mononucleosis-like illness when considering other viral etiologies in the same clinical workup.
`87529`	Infectious agent detection by nucleic acid (DNA or RNA); CMV, direct probe technique	Used when nucleic acid testing (e.g., PCR) is indicated to detect CMV DNA for confirmatory testing, viral load, or testing amniotic fluid.
`87489`	Infectious agent antigen; multiple organisms (if applicable)	Performed when a broader multiplex panel or confirmatory antigen testing is part of the diagnostic workup.