Incidental finding of monoclonal gammopathy in blood donors: a follow-up study

The incidental finding of monoclonal immunoglobulin in the sera of healthy blood donors is a relatively frequent event and in such cases the subjects are commonly deferred permanently from donating blood. However, no follow-up studies of these cases have been published so far.

Since 2000, all regular blood donors at Trieste Blood Bank have undergone annual screening by serum protein electrophoresis. Cases presenting with monoclonal gammopathy between January 2000 and December 2008 were registered and follow-up was performed until December 2010.

Out of 8,197 regular blood donors, monoclonal gammopathy was detected in 104 subjects (1.3%). The median age at detection was 53 years, the median monoclonal protein concentration was 0.2 g/dL and the cumulative follow-up of these cases amounted to 763 person/years. In two cases asymptomatic multiple myeloma was diagnosed within 6 months of detection of the gammopathy and in 14 cases, the monoclonal gammopathy was transient. The remaining 88 cases were classified as having monoclonal gammopathy of undetermined significance (MGUS). Out of these, two events related to monoclonal gammopathy were observed during the follow up: one lymphoma and one light chain deposition nephropathy.

According to current prognostic staging systems, the majority of blood donors with monoclonal gammopathy were classified as having low-risk MGUS and had a very low incidence of lymphoproliferative diseases. Permanent deferral of blood donors with stable MGUS causes about a 1% loss of potential blood donations and it represents a "precautionary measure" that needs to be substantiated and validated.