Allogeneic Processed Thymus Tissue (Rethymic) — Coverage Criteria
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Policy governs coverage and medical necessity criteria for use of allogeneic processed thymus tissue (Rethymic) for immune reconstitution in pediatric congenital athymia patients, and applies to providers submitting claims to Blue Cross NC.
Added applicable revenue codes 0891 and 0892 associated with policy HCPCS code(s).
Added gene/cellular therapy distribution channel management language requiring coordination with Blue Cross NC when distribution from a specialty pharmacy provider may be required.
Minor formatting updates were made to the criteria for clarity.
Coverage and Medical Necessity Criteria
Medically Necessary Criteria
Covered when ALL of the following are met:
ALL of the following
- ONE of: a. Congenital heart defect [medical record documentation required]
- b. Hypoparathyroidism or hypocalcemia requiring calcium replacement [medical record documentation required]
- c. 22q11.2 deletion syndrome [medical record documentation required]
- d. 10p13 hemizygosity [medical record documentation required]
- e. CHARGE syndrome [medical record documentation required]
- f. CHD7 mutation [medical record documentation required]
Duration of approval: 180 days (one treatment course per lifetime)
Exclusion: Treatment with allogeneic processed thymus tissue (Rethymic) is not indicated for the treatment of patients with severe combined immunodeficiency (SCID). Documentation that the patient is not being treated for SCID is required in the medical record to support coverage decisions.
Use of allogeneic processed thymus tissue-agdc (Rethymic) for indications other than immune reconstitution in pediatric patients with congenital athymia is not supported by this policy. Requests for Rethymic for other diagnoses or clinical indications should be considered not medically necessary and require documentation demonstrating the indication aligns with the FDA‑approved use described in the policy.
Applicable Codes and Diagnostic Thresholds
| 0891 | Revenue code - Special Processed Drugs - FDA Approved Cell Therapy |
| 0892 | Revenue code - Special Processed Drugs - FDA Approved Gene Therapy |
Prior Authorization, Documentation, and Provider Requirements
Prior authorization and distribution coordination required
Prior authorization/coordination with Blue Cross NC is required before coverage will be provided; when the benefit requires specialty pharmacy distribution for allogeneic processed thymus tissue (Rethymic), providers must contact and coordinate distribution with Blue Cross NC.
No step therapy requirements specified
This policy specifies that there are no step therapy requirements — providers are not required to attempt or document prior therapies before requesting authorization under this policy.
Required medical record documentation
Medical record documentation must include flow cytometry results showing naïve T‑cell counts/percent (fewer than 50 naïve T‑cells/mm3 or <5% naive phenotype), documentation of complete DiGeorge syndrome features or specified genetic findings, confirmation of FOXN1 deficiency, confirmation the patient is not being treated for SCID, anti‑HLA antibody screening results, and HLA matching when prior transplant occurred.
- Naïve T‑cell flow cytometry: <50 naïve T‑cells/mm3 (CD45RA+, CD62L+) or <5% of total T‑cells
- Documentation of cDGS features (e.g., congenital heart defect; hypoparathyroidism/hypocalcemia requiring calcium replacement; 22q11.2 deletion; 10p13 hemizygosity; CHARGE; CHD7 mutation)
- Confirmation of FOXN1 deficiency
- Evidence patient is not being treated for SCID
- Anti‑HLA antibody screening results prior to treatment
- HLA matching of requested agent to recipient alleles if prior transplant occurred
Documentation and criteria adherence required
Failure to document that the patient meets all listed medical necessity criteria — including age ≤3 years; congenital athymia confirmed by flow cytometry thresholds; required cDGS features or FOXN1 deficiency; not being treated for SCID; anti‑HLA antibody screening; HLA matching when prior transplant; and requested quantity within the maximum units — may result in denial of the request.
Background and Clinical Context
Congenital athymia is a rare condition characterized by deficient thymic function and absence of naïve T‑cells, resulting in impaired T‑cell–mediated immunity. Rethymic (allogeneic processed thymus tissue) is intended for immune reconstitution in pediatric patients with congenital athymia. Coverage under this policy is limited to patients who meet stringent criteria including a diagnosis confirmed by flow cytometry showing fewer than 50 naïve T‑cells/mm3 (CD45RA+, CD62L+) or <5% of total T‑cells with additional required clinical or genetic features (for example, complete DiGeorge syndrome or confirmed FOXN1 deficiency), and other pre‑treatment screening such as anti‑HLA antibody testing. The policy specifies a maximum approval duration of 180 days (one treatment course per lifetime) and a maximum allowable product quantity consistent with coding and dosing guidance.
Key Definitions and Dosing Limits
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