Is Gammunex C (Intravenous Immunoglobulin), 55 grams, every 4 weeks, medically necessary for a patient with diagnoses D80.1 and D83.9?

Medical Necessity Assessment for Gammunex-C in Primary Immunodeficiency

Based on the diagnoses D80.1 (Neonatal neutropenia) and D83.9 (Common variable immunodeficiency, unspecified), Gammunex-C 55 grams IV every 4 weeks is medically necessary if the patient has documented hypogammaglobulinemia with IgG <400-600 mg/dL AND recurrent serious bacterial infections, OR meets specific criteria for immunoglobulin replacement therapy.

Diagnostic Confirmation Required

The primary issue is that D80.1 (Neonatal neutropenia) does not typically require IVIG replacement therapy, while D83.9 (Common variable immunodeficiency) is an FDA-approved indication for Gammunex-C. 1

• Common variable immunodeficiency (D83.9) is an established indication for IVIG replacement therapy and is FDA-approved for Gammunex-C 2, 1
• The diagnosis must be confirmed with documented immunoglobulin deficiency, not just the ICD-10 code 3

Specific Criteria for Medical Necessity

IVIG replacement therapy is indicated when patients meet ANY of the following:

• IgG levels <400 mg/dL regardless of infection history 3
• IgG levels between 400-600 mg/dL AND ≥2 severe recurrent infections by encapsulated bacteria 3
• Life-threatening infection in the setting of immunodeficiency 3
• Documented bacterial infection with insufficient response to antibiotic therapy 3

Dosing Verification

The requested dose of 55 grams every 4 weeks requires patient weight verification:

• FDA-approved dosing for primary immunodeficiency is 300-600 mg/kg every 3-4 weeks 1
• For a 55-gram dose to be appropriate, the patient would need to weigh approximately 92-183 kg (203-404 lbs) at the standard dose range 1
• If the patient weighs significantly less than 92 kg, the dose may be excessive and require adjustment 1

Missing Clinical Information

The physician referral states "no new clinicals submitted from the previous approval" - the following must be documented:

• Current serum IgG trough level to confirm ongoing need for therapy 3, 1
• Documentation of recurrent infections (frequency, severity, causative organisms) since last approval 3
• Patient's actual body weight to verify dose appropriateness 1
• Clinical response to previous IVIG therapy (infection rate reduction, IgG level improvement) 3
• Confirmation that D80.1 diagnosis is accurate or if this should be D80.x (other immunodeficiency) 2, 1

Monitoring Requirements for Continued Therapy

If therapy is approved, the following monitoring is mandatory:

• IgG trough levels every 1-3 months to ensure therapeutic levels are maintained 3, 1
• Target IgG trough level should be >500-600 mg/dL for most patients with primary immunodeficiency 3
• IVIG should be continued until IgG levels normalize AND infections are resolved 3
• Therapy should be discontinued if there is lack of clinical efficacy after 3-6 months 2

Critical Safety Considerations

The following must be assessed before each infusion:

• Renal function monitoring - patients at risk for renal dysfunction should receive IVIG at minimum infusion rate 1
• Thrombosis risk assessment - patients at risk should receive slower infusion rates 1
• IgA deficiency screening - check serum IgA before first dose due to anaphylaxis risk 2, 1
• Maximum infusion rate should not exceed 8 mg/kg/min (0.08 mL/kg/min) for IV administration 1, 4

Recommendation for Authorization

Cannot certify as medically necessary without:

1. Documented IgG level <600 mg/dL (preferably <400 mg/dL) 3
2. Documented history of ≥2 serious bacterial infections if IgG is 400-600 mg/dL 3
3. Patient weight to verify 55-gram dose appropriateness (should be 300-600 mg/kg) 1
4. Clarification of D80.1 diagnosis - this code typically does not require IVIG replacement 2, 1
5. New clinical information since previous approval showing ongoing need for therapy 3

If the patient has confirmed common variable immunodeficiency (D83.9) with documented hypogammaglobulinemia and recurrent infections, then Gammunex-C is medically necessary at the appropriate weight-based dose. 2, 3, 1