SERUM-SOLUBLE IL-6 RECEPTOR CONCENTRATIONS CORRELATE WITH STAGES OF MULTIPLE-MYELOMA DEFINED BY SERUM BETA(2)-MICROGLOBULIN AND C-REACTIVE PROTEIN

Serum soluble interleukin-6 receptor (sIL-6R) concentrations were meas ured in 52 patients with multiple myeloma (MM) and 24 normal controls, using a commercially available immunoenzymatic assay kit. Patients we re staged according to the Bataille et al. myeloma staging system base d on the levels of patients' serum beta(2)-microglobulin and C-reactiv e protein. Twenty-one patients were at stage A of disease, 19 at stage B and 12 at stage C at the time of serum collection for sIL-6R determ ination. Serum sIL-6R concentrations ranged from 15 to 176 ng/ml with a mean of 64.8 +/- 35.9 ng/ml and a median of 58 ng/ml in the entire g roup of patients studied. These values were significantly higher than those of 34.4 +/- 13.3 ng/ml found in the controls (P less than or equ al to 0.001). Patients of stage C had higher sIL-6R levels (94.8 +/- 4 1.2 ng/ml) than patients of stage B (67.7 +/- 31.0 ng/ml) (P < 0.01), and markedly higher than patients of stage A (45.0 +/- 23.1 ng/ml) (P < 0.001). Serum levels of sIL-6R in patients with stage A disease did not differ statistically from those of the controls. A linear positive correlation was observed between serum levels of the receptor and the stage of MM (r = 0.539, P < 0.001). These data strongly suggest that serum sIL-6R concentrations correlate with the stages of MM and may be used as an indicator of the activity of the disease. (C) 1997 Elsevie r Science Ireland Ltd.