Which laboratory finding is indicative of multiple myeloma?

Monoclonal gammopathy is a hallmark laboratory finding indicative of multiple myeloma. It refers to the presence of an abnormal protein produced by monoclonal plasma cells in the bone marrow. This situation arises because multiple myeloma is characterized by the proliferation of a single clone of plasma cells, which produce large amounts of a specific immunoglobulin or portion of it, often identified as M protein in laboratory tests.

In the context of multiple myeloma, the identification of monoclonal gammopathy is significant because it distinguishes the disease from other conditions that can cause elevated protein levels in the blood, such as infections or chronic inflammatory diseases. The detection of monoclonal gammopathy can be done through serum protein electrophoresis, where it appears as a distinct peak, typically in the gamma region of the protein electrophoresis graph.

While increased serum creatinine, hypercalcemia, and anemia are also common in patients with multiple myeloma due to renal impairment, bone involvement, and hematologic effects, respectively, they are not specific findings for the disease. Monoclonal gammopathy directly reflects the underlying pathology of multiple myeloma, making it a definitive indicator of the disease's presence.