The Serum Protein Electrophoresis (SPEP) test is a powerful, deep-dive analysis of your blood's proteins. Think of it as a "protein fingerprint." This advanced test takes your blood serum and separates the proteins into five main groups, displaying them as a specific pattern. It is the gold-standard test for detecting an abnormal protein (a 'monoclonal spike' or 'M-spike'), which is the key marker for diagnosing conditions like Multiple Myeloma. This test provides a detailed, clear-cut pattern, offering your doctor deep insights that a simple protein test cannot.