Revisione e aggiornamento del documento di consenso SIBioC per la ricerca e quantificazione della proteina di Bence Jones
Patrizia Natali1, Giovanni Cigliana2, Marcella Savoia3, Silvia Gelsumini4, Umberto Basile5, Arialdo Vernocchi6, Maria Stella Graziani7, Michele Mussap8, Giovanni Palladini9 1Dipartimento Interaziendale ad Attività Integrata di Medicina di Laboratorio e Anatomia Patologica, Azienda Ospedaliero Universitaria e Azienda Sanitaria Locale di Modena 2Patologia Clinica, Istituto Nazionale Tumori Regina Elena, IRCCS, Roma 3Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università Federico II e Dipartimento Medicina di Laboratorio AOU Federico II, Napoli 4UOC SMeL2 Analisi Chimico Cliniche ASST Papa Giovanni XXIII, Bergamo 5Dipartimento Medicina di Laboratorio, Policlinico Universitario A. Gemelli, IRCCS Università Cattolica del Sacro Cuore, Roma 6Servizio di Medicina di Laboratorio, IRCCS MultiMedica, Milano 7Sezione di Biochimica Clinica, Università di Verona 8Medicina di Laboratorio, Unità di laboratorio molecolare, Dipartimento di Scienze Chirurgiche – Università di Cagliari 9Policlinico San Matteo, IRCCS – Pavia
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 nonHodgkin’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 k and λ 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.