I have seen this type of problem several times since adopting the Sebia electrophoresis system where a filtrate of serum is
applied to the gel through a wick. This results in very "clean" electrophoresis patterns, but a cryoglobulin can be selectively
precipitated and removed by the wick, and the resulting pattern can be depleted of the paraprotein and appear rather normal.
The DTT treatment may or may not help prevent cryoprecipitation... but it seems to have worked well for you.
These types of problems are very difficult to detect and confirm because of the tendency for cryoprecipitation to occur as blood clots, so the
centrifuged serum samples submitted for electrophoresis may already be depleted of the paraprotein.
Note that if the high level of IgM resulted in a highly viscous serum sample, then it is possible that the wick is plugged and no protein/serum is applied to
the gel and the problem is much more obvious.
regards Andrew
Dr. A. Lyon
Saskatoon Health Region,
Univ. Saskatchewan
Saskatoon, SK, Canada
Maybe a cryoglobulin ? Do you spin your samples before applying them onto the gel ?
***************************************************************
Wolfgang Schneider, PhD, CSPQ, FCACB
Chef du service clinique de biochimie
Hôpital du Sacré-Coeur de Montréal
5400, boul. Gouin Ouest
Montréal, Québec H4J 1C5
Canada
Tél.: (514) 338-2222 x 2611
Objet
Vanishing paraprotein
An interesting case of an IgM lambda paraprotein that was not initially visible on serum electrophoresis:
An 83yr old male presented via his GP with a globulin of 39g/L and renal impairment, serum protein electrophoresis was added on by the laboratory. He had low IgA and IgG with a raised IgM of 23.5g/L (0.5-2.0). Electrophoresis showed a marked decrease in gamma globulins but no band. Immunofixation showed lambda light chains but no heavy chain. The raised IgM prompted further investigation and treatment with reducing agent dithiothreitol revealed a paraprotein in the mid-fast gamma, identified as IgM lambda. We’ve not quantified the paraprotein due to concerns over the validity of quantification by scanning densitometry after dithiothreitol treatment.
It’s well known that IgM can polymerise but the strange thing about our case was that there was no band visible at the application point. We’d be interested to know whether anything similar has been seen before?
Vicky
Victoria Clough
Clinical Biochemist
Queen Elizabeth Hospital, Woolwich
South London Healthcare Trust
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