TNFSF14 and monoclonal gammopathy: According to the International Myeloma Working Group updated criteria, serum protein electrophoresis (SPEP) and serum protein immunofixation electrophoresis (SIFE) are commonly used as screening tests in the diagnosis of monoclonal gammopathies, and the findings of SIFE are currently the gold standard for identification of monoclonal immunoglobulins, including both intact immunoglobulins as well as free light-chains.