CPT code 0043U identifies a proprietary immunoblot serology test marketed by IGeneX Inc. that detects IgM antibodies to four recombinant Borrelia protein groups associated with Tick–Borne Relapsing Fever (TBRF). As a PLA code, 0043U is specific to a single manufacturer's assay and signals unique clinical and contracting considerations for payers, providers, and laboratories. Nationally, specialized serologic assays for tick-borne infections are significant due to growing clinician demand for targeted diagnostics in complex cases of suspected Lyme disease and relapsing fever.

Key payers in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise account of what 0043U represents, typical settings where the test is performed, and the scope of coverage considerations tied to proprietary laboratory assays. The publication summarizes benchmark topics relevant to this code, including coding classification as a PLA, implications for laboratory billing and test ordering workflows, and the clinical context for IgM-based Borrelia testing. Where input data is missing, the report notes those gaps as "Data not available in the input."