[Urinary investigations in the diagnosis and monitoring of monoclonal gammopathies in daily practice]

The management of monoclonal gammopathies remains a public health issue with an incidence greater than 3% of the population over 50 years. Laboratory investigations, including urinary investigations play a key role in the diagnosis and monitoring of the patients. Urinary investigations are not recommended when screening monoclonal gammopathies. However, the initial laboratory evaluation of the monoclonal gammopathies systematically relies on renal function and proteinuria assessment. Urinary proteins electrophoresis combined with urinary proteins immunofixation are also recommended in the initial evaluation, with the exception of the Waldenström's disease. In some cases, serum investigations remain negative whereas urinary investigations confirm the presence of a monoclonal component. National and international recommendations have also been published about the monitoring of monoclonal gammopathies. The biological monitoring of monoclonal gammopathy of undetermined significance is mostly done by serum tests. Urinary investigations are commonly included in the response criteria in case of multiple myeloma or AL amyloidosis. Laboratory investigations like serum free light chain assay tend to decrease the need of urinary investigations in the monoclonal gammopathies. However, these urinary investigations currently maintain a leading role in the diagnosis and monitoring of monoclonal gammopathies.