The way that a myeloma patient's bone marrow is tested matters, and running the sample through a plasma cell enrichment process significantly helps increase testing accuracy. 

Plasma cell enrichment is a process that selects out CD138 positive cells from a bone marrow sample. CD138 is primarily found on myeloma cells. This process helps isolate myeloma-specific cells and as a result, helps increase the sensitivity of other tests performed on the bone marrow sample, like FISH testing for genetic mutations or minimal residual disease (MRD) testing. 

Bone marrow samples that are enriched for plasma cells go through a magnetic cell-sorting procedure. They are typically passed through a 0.2-mm filter to remove debris using a MACS system (MACS; Miltenyi Biotec, Bergisch Gladbach, Germany).

They are then incubated with CD138 magnetic microbeads, which allows for separation of CD138 positive cells to be selected and those cells are then loaded onto a MACS column. The CD138 positive cells bind to that column within a MACS magentic separator. The CD138 positive cells are then removed using a liquid. 

Enriching the plasma cells clearly makes for better testing. In a 2013 study at MD Anderson Cancer Center,  plasma cell levels in non-enriched samples ranged from 1%-28% while enriched sample levels were 28%-96%.

In the same study, the FISH test only detected high risk genetic mutations in plasma cell enriched samples. Plasma cell enriched samples also provided the detection of a solitary plasmacytoma and monoclonal gammopathy of undetermined significance (MGUS).

The study authors concluded that using enriched plasma cells can lead to significantly higher detection levels and can improve risk stratification for myeloma patients. 

According to Sagar Lonial, MD of Emory University, all testing should be done on plasma cell enriched cells. Ask your doctor if your lab is using plasma cell enrichment when your bone marrow samples are being tested.