[The CBO professional guideline 'monoclonal gammopathy' (paraproteinemia) (revision)]

The revised guideline 'Monoclonal gammopathy (paraproteinaemia)' of the Dutch Institute for Health Care Improvement (CBO) describes the most recent clinically relevant developments in the field of monoclonal proteins (M-proteins). Criteria with both prognostic and therapeutic significance are established for 'monoclonal gammopathy of undetermined significance' (MGUS) and (smouldering) multiple myeloma. If an M-protein is found incidentally, the therapeutic consequences will be determined mainly by the probability that the M-protein fits in with the diagnosis or the clinical findings in the patient in question, as well as with the type and extent of the monoclonal gammopathy. A myeloma risk score enables the treating physician to judge whether a bone marrow examination and determination of the skeletal status are required. The revised guideline contains specific clinical questions and indications that can be used on the laboratory order forms and which facilitate the interpretation of the test results. The investigation of skeletal abnormalities must fulfill established criteria in order to be able to discriminate between MGUS and multiple myeloma, and for the staging of multiple myeloma. There is no indication for routine MRI, but MRI must be performed urgently in patients with radicular symptoms or a (threatened) transverse lesion. Both cytology and histology of the bone marrow are an essential part of the initial diagnosis and classification of multiple myeloma. Cytogenetic studies of the bone marrow are recommended as well. In the case of unexplained polyneuropathy, an M-protein should be looked for.