Serum Protein ElectroPhoresis (SPEP):
Electrophoresis differentiates proteins based on their size n charge. There are following main types of proteins in plasma : Albumin and Globulins. The Globulins are Alpha (1&2) ,Beta(1&2), and Gamma.
So often we see six spikes: First spike is Albumin->Alpha 1&2->Beta (1&2)-> last spike is Gamma Globulins.
Mainly Gamma Globulins are of primary interest when electrophoresis is ordered.
The most important point to remember is that:
1: Single spike (Monoclonal ) means Malignant cause as Malignancy starts from one cell.
M for Mono,
M for Malignant
Whereas polyclonal means there are many different types of globulins due to various antigens stimulating the immune system and causes are infections, inflammation, autoimmune diseases or liver disease. Solid organ malignancies can also cause polyclonal spikes (but monoclonal spike is never benign).
2: Monoclonal band is due to Lymphocytic Tumours such as Multiple Myeloma, lymphoma, CLL, Waldenstorm Macroglobulinemia, Plasma cell Leukemia, Solitary Plasmacytoma, MGUS, primary amyloidosis.
(These can be further differentiated based on quantity and type of Monoclonal globulin along with bone marrow biopsy and bone lesions etc).
For example: Multiple Myeloma will have more than 15% plasma cells on bone marrow biopsy, bone lesions and may have IgG Type Monoclonal spike. ( I used the word “ may have” as Myeloma can just produce light chains, or heavy chains or may not produce any globulins at all. Waldenstorm has IgM Type Monoclonal spike with less than 10% plasma cells on bone marrow biopsy, no bone lesions, and patients have hyperviscosity. MGUS has less than 3 gm of Monoclonal globulins with no bone lesion, no hyper viscosity etc.
Main and the most common indications for ordering SPEP are when any of these lymphocytic Malignancy is suspected in patients with:
Bone lytic lesions
Renal failure
Anemia / Cytopenia
Secondary autoimmunity
High Globulins
Amyloidosis
Hyperviscosity
Immunodeficiency states etc.