Update of the Italian Society of Clinical Biochemistry (SIBioC) Consensus document on the detection and quantification of the Bence Jones protein.

Update of the Italian Society of Clinical Biochemistry (SIBioC) Consensus document on the detection and quantification of the Bence Jones protein. Bence Jones protein (BJP) refers to urine monoclonal free immunoglobulin light chains produced by the clonal expansion of a plasma cell in the bone marrow. BJP is strongly associated with systemic amyloidosis AL, light chain deposition disease, and multiple myeloma; less frequently, BJP may be recognized either in patients with monoclonal gammopathies of uncertain significance (MGUS) and with other plasma cell dyscrasias or in patients with malignant non-Hodgkin's lymphomas and chronic lymphocytic leukemia. This paper contains updated recommendations for the detection and the measurement of BJP in clinical practice from the Working Group “Proteins” of the Italian Society of Clinical Biochemistry (SIBioC), with specific indications for improving all the steps of the preanalytical, analytical, and postanalytical phases. The first morning void is the urine sample recommended for BJP detection, while 24-hours urine collection is preferred for BJP quantification. Native urine cannot be used for samples with low or very low content in urine total protein; in these cases, samples should be concentrated by using specific disposables, such as ultrafiltration membranes retaining proteins with molecular weight around 10 kDa. The required degree of concentration may vary according to sensitivity of the electrophoretic method utilized and the protein content of the sample. The detection of BJP may be performed directly by the recommended method agarose gel immunofixation (IFE) with specific polyvalent immunoglobulin antisera IgG-IgA-IgM, total  and  light chains; alternatively, an electrophoretic screening may be acceptable to rule out negative test results. However, positive test results should be confirmed by IFE. Tests based on immunometric methods can be used neither as screening test, nor for the BJP quantification; however, it could be useful for monitoring purposes, provided that the renal function of the patient is preserved. BJP measurement should be performed by the densitometric scanning of the electrophoretic peak corresponding to BJP, and results should be expressed as ratio of the BJP peak percentage to the urine total protein. Test results should be always integrated by standardized interpretative comments included in the laboratory reports.