What laboratory tests are recommended for patients undergoing plasma pheresis (plasma exchange) for myasthenia gravis?

Laboratory Monitoring for Plasma Pheresis in Myasthenia Gravis

Before initiating plasmapheresis in myasthenia gravis patients, check serum IgA levels to prevent potentially fatal anaphylaxis, along with baseline acetylcholine receptor antibodies, complete blood count, coagulation studies, and serum protein levels including albumin and immunoglobulins. 1

Pre-Procedure Essential Labs

Mandatory Safety Screening

• Serum IgA levels: Must be checked before IVIG or plasmapheresis, as IgA deficiency can lead to severe anaphylactic reactions 1
• Coagulation studies: Required to assess bleeding risk during vascular access and procedure

Baseline Disease Markers

• Acetylcholine receptor (AChR) antibodies: Establish baseline levels to monitor treatment response 1, 2, 3
• Anti-striated muscle antibodies: Particularly important in thymoma-associated cases 1, 2
• MuSK antibodies: Check if AChR antibodies are negative 2
• LRP4 antibodies: Additional testing if seronegative for AChR and MuSK 2

Baseline Protein and Metabolic Panel

• Serum protein electrophoresis with immunoglobulins (IgG, IgA, IgM): Track depletion during exchanges 4
• Albumin and total protein: Monitor replacement needs 4, 5
• Complete blood count: Baseline hematologic status 2

Concurrent Cardiac and Muscle Assessment

Rule Out Myocarditis/Myositis

• Creatine phosphokinase (CPK): Elevated levels suggest concurrent myositis and necessitate cardiac evaluation 1, 2
• Aldolase, ESR, CRP: Additional markers for inflammatory myositis 2
• Troponin T: If CPK elevated or respiratory insufficiency present 2
• ECG and transthoracic echocardiogram: Required if elevated CPK/troponin or respiratory compromise to exclude myocarditis 1, 2

This is critical because patients with concurrent myocarditis and myasthenia gravis have an ominous prognosis with high mortality rates 6

Respiratory Function Assessment

Pulmonary Function Tests

• Negative inspiratory force (NIF): Baseline measurement essential 1, 2
• Vital capacity (VC): Monitor using the "20/30/40 rule" (VC <20 mL/kg, max inspiratory pressure <30 cmH₂O, or max expiratory pressure <40 cmH₂O indicates respiratory failure risk) 1, 2

Monitoring During Treatment Course

Serial Antibody Measurements

• AChR antibody titers: Should be measured serially during plasmapheresis cycles, as clinical improvement correlates with antibody reduction to approximately 21% of baseline levels 3
• Clinical relapses associate with antibody rebound 3

Protein Depletion Monitoring

• Immunoglobulin levels (IgG, IgA, IgM): Daily plasmapheresis produces greater reductions (IgA 81.5%, IgM 95.6%, globulin 63.2%) compared to alternate-day schedules 4
• Albumin and total protein: Monitor for excessive depletion requiring replacement 4, 5

Common Pitfalls to Avoid

• Never administer IVIG or plasmapheresis without checking IgA levels first—this is a potentially fatal oversight 1
• Do not rely solely on antibody levels to guide treatment: Even seronegative patients may improve with plasmapheresis, and antibody fluctuations correlate poorly with clinical response 7
• Immediately discontinue contraindicated medications: IV magnesium (absolutely contraindicated), beta-blockers, fluoroquinolones, aminoglycosides, and macrolides can precipitate respiratory failure 2
• Monitor for hypotension during exchanges: Occurs in approximately 2.7% of sessions but is generally reversible 4, 5