When should serum protein electrophoresis (SPEP) with reflex immunofixation be ordered in the work‑up of lymphoma?

When to Order SPEP with Reflex Immunofixation in Lymphoma Work-Up

Serum protein electrophoresis (SPEP) with reflex immunofixation should be ordered as part of the mandatory initial staging work-up for marginal zone lymphomas (all subtypes) and is useful in selected cases for other lymphoma types when there is clinical suspicion of a monoclonal component or concurrent plasma cell disorder.

Primary Indication: Marginal Zone Lymphomas

For all marginal zone lymphoma (MZL) subtypes (extranodal, nodal, and splenic), SPEP is mandatory in the initial work-up 1. The 2020 ESMO guidelines explicitly list "protein electrophoresis" along with "serum and urine immunofixation" as required baseline investigations 1. This is particularly important because:

• A small monoclonal component (usually IgM) may be detected in nodal MZL, requiring differentiation from lymphoplasmacytic lymphoma 1
• Up to 25-50% of non-gastric extranodal MZL cases present with disseminated disease 1
• The presence of a monoclonal protein can influence diagnostic considerations and differential diagnosis

Secondary Indications: Other Lymphoma Types

For other lymphoma subtypes, SPEP with immunofixation is listed as "useful in selected cases" rather than mandatory 2. Consider ordering when:

• There is clinical suspicion of concurrent plasma cell disorder
• Unexplained hyperglobulinemia is present
• The patient has symptoms suggesting hyperviscosity
• Differential diagnosis includes lymphoplasmacytic lymphoma/Waldenström's macroglobulinemia
• There are unexplained renal or neurologic symptoms that could suggest amyloidosis

Important Caveats

Do not confuse lymphoma work-up with myeloma work-up. The evidence provided predominantly addresses plasma cell disorders (multiple myeloma, MGUS, smoldering myeloma) where SPEP with immunofixation is absolutely mandatory for diagnosis 3, 4, 5. In these conditions, SPEP and immunofixation are used to:

• Detect and characterize the M-protein 3, 4
• Quantify disease burden 4
• Monitor treatment response 6, 7

For lymphomas other than MZL, the primary staging modality is imaging (PET-CT for FDG-avid lymphomas, CT for others) combined with bone marrow biopsy, not serum protein studies 8.

Practical Algorithm

1. If evaluating marginal zone lymphoma (any subtype): Order SPEP with reflex immunofixation as part of mandatory staging 1

2. If evaluating other lymphoma types:

   • Review clinical presentation for features suggesting concurrent monoclonal gammopathy
   • Check quantitative immunoglobulins first (already part of standard work-up)
   • Order SPEP with reflex immunofixation only if there is polyclonal or monoclonal elevation, or specific clinical concern

3. Reflex immunofixation is preferred over routine immunofixation to avoid unnecessary testing 9, 10. The pathologist should reflex to immunofixation when SPEP shows:

   • Discrete monoclonal peak
   • Suspicious β-region findings 11
   • Hypogammaglobulinemia with small abnormal band
   • Any qualitative abnormality suggesting monoclonal protein

Common Pitfall

Avoid reflexive ordering of "the full myeloma panel" (SPEP, immunofixation, free light chains, 24-hour urine) for all lymphoma patients. This leads to unnecessary testing and cost 10. Recent data shows that when SPEP, immunofixation, and free light chains are ordered simultaneously without clinical indication, the vast majority are negative 9. Order these tests based on the specific lymphoma subtype and clinical context, not as a blanket approach.