Summary & Overview
CPT 83873: Myelin Basic Protein in Cerebrospinal Fluid Assay
CPT code 83873 designates a laboratory assay that measures myelin basic protein (MBP) in cerebrospinal fluid, a biomarker used in the clinical evaluation of demyelinating disorders such as multiple sclerosis. This code captures a specialized CSF biomarker test performed by clinical laboratories supporting neurology practices and hospital services. Nationally, accurate capture of this service affects clinical coding, laboratory billing, and epidemiologic tracking of workups for suspected MS.
Key payers addressed in this overview include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise explanation of what the code represents, the typical clinical context and sites of service, and the categories of information commonly reviewed when assessing coverage and billing practices for CSF MBP testing. The publication covers benchmarks and policy-relevant items readers should expect to review, including reimbursement considerations, coding guidance, and clinical context for ordering the test.
This summary is written for a national audience and is intended to orient billing managers, laboratory directors, and clinician coders to the purpose and usage of CPT code 83873, and to identify the types of materials and updates that are typically relevant when monitoring coverage and coding for CSF MBP assays.
Billing Code Overview
CPT code 83873 reports a laboratory measurement of myelin basic protein (MBP) in cerebrospinal fluid (CSF). The test quantifies MBP concentration to assist clinicians evaluating patients with neurological symptoms suggestive of multiple sclerosis (MS) or other demyelinating conditions.
Service type: Clinical laboratory test — cerebrospinal fluid biomarker assay
Typical site of service: Hospital laboratory, outpatient laboratory, or specialized neurology clinic with CSF testing capability
Data not available in the input.
Clinical & Coding Specifications
Clinical Context
A 34-year-old patient presents to neurology with new-onset paresthesia, intermittent visual blurring, and gait instability. The neurologist obtains a detailed neurologic exam and orders brain MRI with and without contrast followed by lumbar puncture to analyze cerebrospinal fluid (CSF). CSF is sent to the clinical laboratory for biochemical and immunologic testing, including measurement of myelin basic protein (MBP) by laboratory analysis 83873. The laboratory analyst performs the quantitative MBP assay on the CSF specimen and reports concentration to the ordering provider. Results are integrated into the clinical workflow to assist in diagnosing active demyelination associated with multiple sclerosis or other inflammatory CNS disorders; they are considered alongside MRI findings, oligoclonal band testing, and clinical presentation. Typical site of service: hospital outpatient laboratory, reference diagnostic laboratory, or hospital inpatient laboratory when CSF is collected during admission. Service type: clinical laboratory quantitative assay of cerebrospinal fluid biomarker.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when billing only the professional interpretation component if applicable (rare for lab-only assays where professional interpretation is reported separately). |