CPT code 84437 designates a laboratory assay for measuring thyroxine (T4) in specimens that require elution, a process commonly applied to neonatal dried blood spots. The code captures a technical pre-analytic step and quantitative analysis necessary for neonatal thyroid screening and other clinical contexts where whole blood has been absorbed to a substrate and must be recovered for testing. Nationally, accurate coding for this procedure supports newborn screening programs, laboratory reporting, and consistent payment across facilities.

Key payers addressed in this analysis include Aetna, Blue Cross Blue Shield, Cigna, UnitedHealthcare, and Medicare. Readers will find a clinical context for when elution-based T4 testing is used, an outline of typical sites of service (clinical and hospital laboratories), and practical information about common modifiers and billing considerations. The publication also provides benchmark-oriented content and policy updates relevant to laboratory billing and newborn screening workflows. This summary equips laboratory managers, coding professionals, and policy staff with a concise reference on CPT code 84437, its clinical role, and the payer landscape affecting reimbursement and claims processing.

Data not available in the input: Associated taxonomies, ICD-10 diagnoses, related codes, and detailed service line information.