title: Diagnostic value of serum IL-6 level in monoclonal gammopathies.
abstract: The serum level of IL-6 was reported to reflect disease severity in patients with multiple myeloma. We used a specific radioimmunoassay to measure the level of IL-6 in 239 serum samples in which a monoclonal gammopathy was identified for the first time. The same sample was used for the measurement of serum C reactive protein and serum albumin. Then, an inventory of clinical and biological features allowed us to classify these patients into five groups: monoclonal gammopathy of undetermined significance (MGUS:128), multiple myeloma (MM:66), Waldenström's macroglobulinaemia (WM:27), non-Hodgkin's lymphoma (NHL:11) and chronic lymphocytic leukaemia (CLL:7). The number of patients with serum IL-6 (S-IL-6) level > 0.335 ng/ml (upper limit in normal sera) was significantly higher in the MM group (35%; Confidence Interval (CI) 23.5-46.5) compared with the MGUS group (15%; CI 8.8-21.2). The distribution of S-IL-6 levels was also significantly different between the groups (Mann-Whitney test: P < 0.01). High S-IL-6 levels were measured in 5/11 patients with NHL and 9/27 patients with WM. The distribution of S-IL-6 levels in these groups was the same as that in MGUS or MM groups. In patients with MM, elevated S-IL-6 levels were associated with haemoglobin level < 100 g/l (P < 0.005), bone marrow plasmocytosis > 50% (P < 0.005) and stages II and III in the Durie & Salmon staging system (P < 0.005). The S-IL-6 level was also related to light chain component excretion in urine (P < 0.01) and M component serum level for IgA (P < 0.01). In patients with MGUS, the S-IL-6 level correlated with serum CRP level (P < 0.05), serum lactate dehydrogenase (P < 0.05) and serum ferritin (P < 0.01). We conclude that the S-IL-6 level is a marker of high tumour burden in multiple myeloma. However, S-IL-6 level can be increased in patients with MGUS in relation to inflammatory parameters. Therefore the S-IL-6 level does not demonstrate high predictive value for the diagnosis of MM in patients with newly identified monoclonal gammopathy.
authors.affiliation: Laboratory of Biochemistry, C.H.U. Le Bocage, Dijon, France.
authors.forename: L
authors.initials: L
authors.lastname: DuVillard
authors.forename: M
authors.initials: M
authors.lastname: Guiguet
authors.forename: R O
authors.initials: RO
authors.lastname: Casasnovas
authors.forename: D
authors.initials: D
authors.lastname: Caillot
authors.forename: V
authors.initials: V
authors.lastname: Monnier-Zeller
authors.forename: A
authors.initials: A
authors.lastname: Bernard
authors.forename: H
authors.initials: H
authors.lastname: Guy
authors.forename: E
authors.initials: E
authors.lastname: Solary
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002097:C-Reactive Protein / Q000032:analysis; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000097:blood / Q000175:diagnosis; D008228:Lymphoma, Non-Hodgkin / Q000097:blood / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000097:blood / Q000175:diagnosis; D010265:Paraproteinemias / Q000097:blood / Q000175:diagnosis*; D012709:Serum Albumin; D008258:Waldenstrom Macroglobulinemia / Q000097:blood / Q000175:diagnosis
chemical_list: D015850:Interleukin-6; D012709:Serum Albumin; D002097:C-Reactive Protein