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CPT 82787: IgG Subclass Quantitation (Serum or CSF)
CPT code 82787 represents quantitative measurement of immunoglobulin subclasses, most commonly the four IgG subclasses (IgG1–IgG4), performed on serum or cerebrospinal fluid. This test aids in diagnosing subclass-specific antibody deficiencies and refining immunodeficiency evaluations, making it a relevant diagnostic tool across hospital and clinical laboratory settings nationwide. Payers in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will learn the clinical context of the assay, typical sites of service, and the types of diagnostic scenarios that prompt ordering of subclass testing. The publication provides benchmarks and payer coverage perspectives where available, summarizes coding and billing implications for laboratory services, and highlights policy or reimbursement updates affecting immunology testing. It also outlines common modifiers associated with laboratory billing and notes when further clinical documentation may be needed for medical necessity determinations. Data not available in the input is clearly indicated where applicable.
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Billing Code Overview
CPT code 82787 describes laboratory testing that measures the levels of immunoglobulin subclasses in a serum or cerebrospinal fluid specimen. The assay quantifies each IgG subclass (IgG1, IgG2, IgG3, IgG4) and may be ordered to evaluate immune function or to investigate subclass-specific antibody deficiencies.
Service type: Laboratory diagnostic test — immunology/serology
Typical site of service: Clinical laboratory or hospital laboratory, with specimens collected in outpatient phlebotomy settings, inpatient units, or lumbar puncture procedures when testing cerebrospinal fluid.