Find below some definitions of the most frequently used terms when discussing topics around minimal residual disease. Some of them will be further explained throughout the guide. 

Plasma cells: A type of white blood cell that normally produces antibodies to fight infection. In myeloma, these cells become cancerous and produce abnormal proteins.

Bone marrow: The soft, spongy tissue inside your bones where blood cells, including plasma cells, are made.

Response to myeloma treatment: How well your body reacts to therapy, measured by the reduction in myeloma cells and other disease markers in your body.

MRD (Minimal or Measurable Residual Disease): The small number of myeloma cells that may remain in your body after treatment, even when standard tests show a complete response.

Sensitivity levels: The ability of a test to detect very small numbers of myeloma cells. Higher sensitivity means the test can find smaller amounts of remaining cancer cells.

10⁻⁴ to 10⁻⁵ sensitivity: A measure of test precision that means the test can find one myeloma cell among 10,000 to 100,000 normal cells.

Next-generation sequencing (NGS): A sophisticated DNA testing method that can identify and count specific myeloma cells at very low levels in bone marrow samples.

Cytometry (Flow cytometry): A testing technique that uses laser technology to identify and count specific types of cells, including myeloma cells, in bone marrow samples.