Serum protein electrophoresis (SPEP) is a blood test that separates the proteins in serum into distinct fractions based on their electrical charge. The result is reported as a tracing with five main regions: albumin, alpha-1 globulin, alpha-2 globulin, beta globulin, and gamma globulin. Each region reflects different protein populations with distinct clinical significance.

What SPEP is used for:

Detecting monoclonal proteins (M-spikes) — the hallmark finding in MGUS, smoldering myeloma, and multiple myeloma
Evaluating unexplained changes in total protein or globulin levels
Screening for hypergammaglobulinaemia (polyclonal elevation) in chronic infection, autoimmune disease, or liver disease
Monitoring known plasma cell disorders over time

How results are reported: Most SPEP findings are reported as fractions (in g/dL) and as a visual tracing. A normal gamma region shows a broad, smooth curve. An abnormal monoclonal protein produces a sharp, narrow spike — the M-spike — in the gamma or beta region. Individual protein fractions (albumin, alpha-1, alpha-2, beta, gamma) are reported separately alongside the electrophoresis interpretation.

Common SPEP findings in this category:

M-spike (monoclonal spike) — sharp peak indicating clonal immunoglobulin production; evaluated for MGUS, smoldering myeloma, or active myeloma
Abnormal protein band — a detected band requiring further characterisation by immunofixation
Hypogammaglobulinaemia — reduced gamma globulins suggesting immunodeficiency or immunosuppression
Polyclonal gammopathy — broad gamma elevation consistent with chronic infection, autoimmune disease, or liver cirrhosis
Albumin fraction — the dominant protein band; low albumin in the context of elevated globulins affects the albumin:globulin ratio

Related tests: SPEP findings typically prompt follow-up with serum immunofixation electrophoresis (IFE) to characterise the immunoglobulin class and light chain type, serum free light chain assay, and urine protein electrophoresis (UPEP) to detect Bence Jones protein. Together these tests form the core laboratory evaluation for plasma cell disorders.

Biomarkers included in this panel:

Abnormal Protein Band 1

Serum Plasma

The biomarker Abnormal Protein Band 1 is part of a blood test called "Protein Electrophoresis". Protein electrophoresis is a test that measures specific proteins in the blood. The test separates proteins in the blood base

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M-Spike

Serum

The M-spike (monoclonal spike or M-protein) is detected on serum protein electrophoresis (SPEP) as a sharp, narrow band indicating an abnormal accumulation of a single type of immunoglobulin. A normal result is "not observed" or "not d

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Serum protein electrophoresis (SPEP)

Biomarkers included in this panel:

Abnormal Protein Band 1

M-Spike

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