Serum interleukin-6 has no discriminatory role in paraproteinaemia nor a prognostic role in multiple myeloma

We determined interleukin-6 (IL-6) levels in the serum of 212 well-defined patients with newly diagnosed paraproteinaemia and evaluated its discrimina tory value and prognostic role in multiple myeloma (MM). Results were compa red with serum neural cell adhesion molecule and beta-2-microglobulin, both established prognostic MM markers. Paraproteinaemia-related diagnoses were : MM (60), other haematological diseases (46), solid tumours (35), autoimmu ne diseases (17) and monoclonal gammopathy of unknown significance (MGUS) ( 54). The range of IL-6 levels in all diagnostic groups overlapped widely an d did not serve as a discriminatory marker in newly diagnosed paraproteinae mia even when patients with infection or fever (42) were excluded, In MM hi gh IL-6 levels (greater than or equal to 50 pg/ml) were not associated with a shorter survival (P=0.24). We compared our results with 20 published stu dies on serum IL-6 in paraproteinaemia and/or MM. IL-6 data have to be rela ted to the assay used (bio- or immunoassay) and to the status of MM (newly diagnosed, during therapy, progressive disease). We conclude that serum IL- 6 is not specific for paraproteinaemia-related diseases and will not serve as a reliable discriminatory or prognostic marker in paraproteinaemia and M M.