[beta2-Microglobulin and monoclonal gammapathies (author's transl)].

145 Determinations of beta2-microglobulin (beta2m) have been realized in 111 patients with a monoclonal gammapathy. The level of beta2m is significantly higher (p = 0,0001) in the group with monoclonal gammapathy (M = 4,75 mg/l +/- 5,62) than in normal subjects (M 1,38 mg/l +/- 0,38). In a group with monoclonal gammapathy with renal failure, the level of beta2m is higher (M = 7,07 mg/l +/- 7,76) than in a group with renal failure alone (M = 3,45 mg/l +/- 1,91). The difference is significant (p = 0,005). The level of beta2m is higher in IgA monoclonal gammapathies (M = 5,61 mg/l) than in IgG (M = 4,18 mg/l) or IgM (M = 4,37 mg/l) gammapathies, but the differences of the means between the three groups are not significant. The assay of beta-2m does not allow to distinguish myeloma (M = 3,18 mg/l +/- 1,83) from benign monoclonal gammapathy (M = 3,22 mg/l +/- 1,32) and is not useful when the diagnosis is difficult.