Paraprotein-induced spurious hypercalcaemia: diagnostic pitfalls in two cases

Abstract This brief report describes 2 cases in which paraprotein caused spurious biochemistry results. In both cases standard laboratory measurements of calcium indicated the patients were hypercalcaemic and had significantly raised Vitamin D concentrations in serum. However, use of alternative measurements of calcium and vitamin D showed that these results were spurious. Clinicians looking after patients with significant paraprotein concentrations or other significant protein abnormalities should be aware of the possibility of assay interference when reviewing their biochemistry results. This awareness can be vital in avoiding unnecessary investigations or treatments, thus not only saving resources but also protecting patients from harm that may be caused by inappropriate therapies.