What lab values indicate the need for plasmapheresis?

Lab Values as Indications for Plasmapheresis

Specific lab values that indicate the need for plasmapheresis include rapidly increasing serum creatinine, presence of anti-GBM antibodies with renal dysfunction, high GM-CSF autoantibody titers in refractory pulmonary alveolar proteinosis, and elevated IgM levels (≥5,000 mg/dL) causing hyperviscosity. 1

Renal Indications

ANCA-Associated Vasculitis

• Rapidly increasing serum creatinine - Plasmapheresis is recommended for patients with:
  • Rapidly deteriorating renal function 1
  • Patients requiring dialysis 1
  • Serum creatinine >5.8 mg/dL (strongest evidence from MEPEX trial) 1

Anti-GBM Disease (Goodpasture's Syndrome)

• Positive anti-GBM antibodies with concurrent renal dysfunction 1
• Plasmapheresis is indicated as part of initial treatment along with immunosuppression

Overlap Syndromes

• Concurrent ANCA and anti-GBM antibodies - Plasmapheresis is suggested for patients with this overlap syndrome 1

Pulmonary Indications

Diffuse Pulmonary Hemorrhage

• Hemoptysis with declining oxygen saturation and pulmonary infiltrates on imaging 1
• Recommended regimen: 60 mL/kg volume replacement, daily until bleeding stops, then every other day for a total of 7-10 treatments 1

Pulmonary Alveolar Proteinosis (PAP)

• High GM-CSF autoantibody titers in autoimmune PAP 1
• Indicated for patients who:
  • Remain significantly symptomatic
  • Require high-flow supplemental oxygen (≥4 L/min)
  • Need two or more whole lung lavages over a one-year period
  • Have failed GM-CSF and rituximab therapies 1

Hematologic Indications

Hyperviscosity in Waldenström's Macroglobulinemia

• IgM levels ≥5,000 mg/dL (even if asymptomatic) 1
• Symptomatic hyperviscosity regardless of specific IgM level 1
• Should be performed before rituximab administration to prevent IgM flare 1

Thrombotic Thrombocytopenic Purpura (TTP)

• Severe thrombocytopenia with microangiopathic hemolytic anemia 2
• Elevated LDH and schistocytes on peripheral blood smear
• Low ADAMTS13 activity (<10%)

Neurologic Indications

Autoimmune Encephalitis

• Positive neural autoantibodies (e.g., NMDAR, LGI1) with encephalopathy 1
• Consider when other therapies have failed or rapid improvement is needed

Important Clinical Considerations

1. Timing is critical - In conditions like pulmonary hemorrhage or rapidly progressive glomerulonephritis, early initiation improves outcomes

2. Monitoring during treatment:

   • For hyperviscosity: Monitor IgM levels
   • For ANCA vasculitis: Monitor serum creatinine and clinical symptoms
   • For pulmonary hemorrhage: Monitor oxygen saturation and hemoptysis

3. Potential complications:

   • Hemodynamic shifts
   • Infection risk
   • Thrombosis
   • Removal of therapeutic medications (e.g., rituximab)

4. Common pitfalls:

   • Delaying plasmapheresis in life-threatening conditions
   • Not collecting appropriate samples before initiating plasmapheresis (may alter antibody test results)
   • Failure to provide appropriate replacement fluids

5. Practical tip: When using plasmapheresis with rituximab, administer rituximab after completing plasmapheresis sessions to prevent removal of the therapeutic antibody 1

Remember that plasmapheresis should be considered as part of a comprehensive treatment approach that typically includes appropriate immunosuppressive therapy for the underlying condition.