Pseudohyperphosphataemia in multiple myeloma.

Two cases of spurious hyperphosphataemia in patients with multiple myeloma are presented. An unreduced phosphomolybdate method without dialysis was used and the falsely raised values are shown to be due to the formation of a proteinaceous suspension in the reaction mixture. Such interference may be more prevalent than is generally recognized, and care should be taken to identify the problem in patients with myeloma.