Contradictory Phenomenon Between Serum Separator Tube and Plasma Tube: A Case Report

Separator gels in blood collection tubes are used to separate serum from clotted whole blood or plasma from cells. Here we present a case of a patient with a contradictory phenomenon between the serum separator tube and the plasma tube. The serum separator tube showed mixed serum and separator gel and distinctly less serum. However, the plasma tube showed fewer cells. Laboratory study revealed an IgG level of 78.9 g/L. Serum immunofixation electrophoresis analysis identified the abnormal pattern as a dense IgG band with a corresponding dense light chain band of λ. Bone marrow smear showed 53% proplasmacytes. The patient was diagnosed with multiple myeloma. The marked hyperproteinemia, especially hyperimmunoglobulinemia, may have resulted in the density alteration of serum that was mixed or located above the separator gel. This phenomenon is also seen in patients injected with iodinated radiologic contrast media such as iohexol and in patients on hemodialysis with a concentrated sodium citrate solution.