Unclassified green dots on nucleated red blood cells (nRBC) plot in DxH900 from a patient with hyperviscosity syndrome.

OBJECTIVES: Analytical interferences, caused by antibodies, often go unnoticed and require a deep understanding of analyzer principles in the correct clinical context. METHODS: A case report details a 56-year-old man with symptoms of hyperviscosity syndrome (HVS) due to multiple myeloma. RESULTS: The DxH 900 analyzer revealed abnormalities in the nucleated red blood cell (nRBC) graph, attributed to a high concentration of IgA kappa. Immediate plasmapheresis successfully treated HVS, reducing the monoclonal component and eliminating the aberrant green signal. CONCLUSIONS: In the appropriate clinical context, the recognition of analytical interferences is necessary for accurate clinical interpretation, and it is only possible with knowledge of the analytical principles of the instruments. In this case, the high concentration of IgA kappa generated an aberrant green signal in the VCSm.