A case series of falsely elevated serum troponin I in Fabry disease secondary to macrotroponin

Abstract

Background: Electrophoretic quantification of paraproteins varies between laboratories, particularly for paraproteins that comigrate with normal beta-region proteins. To reduce inter-laboratory variability, new guidelines for standardised reporting recommend quantitating beta-migrating paraproteins with the entire beta-region. 1 For laboratories currently quantitating beta-1 and beta-2 migrating paraproteins separately, paraprotein estimations are likely to increase on total beta-quantification, but the magnitude of this has not been assessed. Aim: To compare measurement of beta-migrating paraproteins using total beta-quantification to that of beta-1 or beta-2 quantification. Methods: Beta-migrating paraproteins were re-quantitated retrospectively in 6 months of capillary zone electrophoresis data. Results: Of 2054 paraproteins examined, 175 (8.5%) migrated in the beta-region. When re-quantitated with the total betaregion, the median increase in beta-1 and beta-2 migrating paraprotein concentration was 2.0 g/L (IQR 1.6,2.5) and 4.2 g/ L (IQR 3.4,4.9) respectively. For small paraproteins, this represented two-to three-fold increases in paraprotein concentration. Discussion: Adoption of total beta-quantification may significantly increase estimated paraprotein concentrations. This is most conspicuous for bands migrating in the beta-2 region but also significant for beta-1 migrating proteins. For both, impact is greatest with small paraproteins. Such increases may be interpreted as progression of disease and trigger further investigations.