Summary & Overview
CPT 86331: Qualitative Immunodiffusion by Ouchterlony Method
CPT code 86331 represents a qualitative immunodiffusion assay using the Ouchterlony method to detect specific antigens or antibodies in a patient specimen. This laboratory procedure is reported once per antigen or antibody tested and is used in clinical immunology to identify immune responses to pathogens or to characterize specific proteins. Nationally, use of this code reflects diagnostic workflows in infectious disease, autoimmune evaluation, and immunology research contexts where qualitative diffusion techniques remain clinically relevant.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of clinical context for CPT code 86331, typical sites of service, and the types of laboratory settings that commonly report the code. The publication provides benchmark-oriented content such as common payer coverage patterns and coding considerations, a concise explanation of when the test is reported (once per antigen or antibody), and comparisons to related laboratory methods where qualitative immunodiffusion may be selected.
This summary is intended to give billing and laboratory managers, coding staff, and policy analysts a clear, national-level view of CPT code 86331, its clinical purpose, and the payer landscape relevant to its use. Data not available in the input: associated taxonomies, ICD-10 diagnoses, related codes, and detailed payer-specific policy language.
Billing Code Overview
CPT code 86331 describes a qualitative immunodiffusion test performed by the Ouchterlony method to evaluate a patient sample for specific antigens or antibodies (immunoglobulins). The procedure is reported once for each antigen or antibody tested.
Service type: Laboratory diagnostic immunology test (qualitative immunodiffusion)
Typical site of service: Clinical laboratory or hospital laboratory
Clinical & Coding Specifications
Clinical Context
A patient with subacute onset of unexplained muscle weakness and suspected autoimmune neuropathy presents to a neurology clinic. The clinician orders serologic testing to identify specific antibodies against neural antigens to support a diagnosis such as myasthenia gravis, peripheral neuropathy with immune etiology, or paraneoplastic syndromes. A phlebotomy technician collects a blood sample which is sent to the clinical immunology laboratory. A medical laboratory scientist or technologist performs a qualitative immunodiffusion assay using the Ouchterlony method to detect precipitating antigen–antibody complexes for one or more specific antigens/antibodies. The laboratory documents results as positive or negative for each tested antigen/antibody and reports findings back to the ordering clinician for correlation with clinical exam, electrophysiology, or imaging. Billing reports 86331 once per antigen or antibody tested; the workflow includes specimen accessioning, assay setup, incubation, interpretation of precipitin lines, result documentation, and result transmission to the ordering provider or electronic medical record. Typical sites of service include outpatient phlebotomy collection centers, hospital outpatient laboratories, or independent clinical laboratories that perform specialized immunology testing.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when only the professional interpretation component is billed by the pathologist or laboratory physician. |