Summary & Overview
HCPCS Level II J1931: Injection, laronidase, 0.1 mg
HCPCS Level II code J1931 denotes the injection of laronidase in 0.1 mg units, used to bill for enzyme replacement therapy administrations. This code matters nationally because laronidase is a specialized biologic therapy for rare lysosomal storage disorders, and accurate coding affects coverage decisions, site-of-service billing, and beneficiary access to care. The analysis covers major national payers including Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare.
Readers will learn how J1931 functions as the billing vehicle for laronidase administrations, the typical clinical settings where it is delivered (outpatient infusion centers and hospital outpatient departments), and which payer types are involved in coverage and payment determinations. The publication summarizes available benchmarks and policy considerations relevant to biologic infusion billing, highlights common billing modifiers used with HCPCS medication codes, and provides clinical context for why precise unitization (0.1 mg increments) is important for dosing and reimbursement. Data not available in the input where payer-specific rates, utilization metrics, or associated ICD-10 diagnoses would normally be reported.
Billing Code Overview
HCPCS Level II code J1931 represents an injection of laronidase supplied in increments of 0.1 mg. This code is used to report administration of the enzyme replacement therapy laronidase, a recombinant human alpha-L-iduronidase, for patients requiring this specific biologic therapy.
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Service type: Medication administration (intravenous infusion/injection of a biologic)
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Typical site of service: Outpatient infusion center or hospital outpatient department; may also be administered in specialty clinics depending on clinical setting and payer policies.
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Clinical & Coding Specifications
Clinical Context
A pediatric or adult patient with confirmed mucopolysaccharidosis type I (MPS I) attends an infusion center for enzyme replacement therapy with laronidase. The patient arrives for a scheduled outpatient infusion; pre-infusion activities include vital signs, review of prior infusion tolerance, allergy check, and verification of weight and dose calculation. A nurse prepares the reconstituted product and performs IV access placement (peripheral or via central venous catheter if indicated). Laronidase is administered intravenously at the prescribed dose, billed as J1931 per 0.1 mg increment, with continuous monitoring for infusion reactions. Post-infusion observation occurs for a period determined by patient history (typically 30–60 minutes) and documentation of tolerance, vital signs, and any medications administered for infusion reactions (for example, antihistamines or steroids) is completed. Billing occurs for the drug using J1931 units corresponding to the milligram dose given; appropriate modifiers are appended as indicated by the service circumstances (e.g., place of service, multiple procedures, discontinued services, patient non-coverage indicators). Typical sites of service are outpatient hospital infusion centers, physician offices with infusion capability, and specialty infusion clinics. Typical patient scenario: a 7-year-old child with established diagnosis of MPS I receiving weekly or every-other-week laronidase infusions via peripheral IV in an ambulatory infusion center, with prior history of mild infusion-related urticaria managed with premedication.
Coding Specifications
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