The Bence Jones Protein qualitative test is a laboratory analysis used to detect free monoclonal immunoglobulin light chains (kappa or lambda) in urine. These abnormal proteins are frequently produced in excess by plasma cell disorders, most notably multiple myeloma, as well as Waldenström macroglobulinemia and amyloidosis. Detecting Bence Jones proteins aids clinicians in diagnosing and monitoring these conditions. While a qualitative test provides a straightforward positive or negative result to indicate their presence, it serves as a critical initial screening marker that often prompts further quantitative evaluation and comprehensive clinical workups for underlying monoclonal gammopathies.