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Clinical Significance of Abnormal Serum Free Light Chain Ratio: Diagnostic Confusion or Underlying Monoclonality? by Sun Young Cho, You Sun Nam, Hwi-Joong Yoon, Hee Joo Lee, Tae Sung Park

Background: The spectrum of laboratory tests used to detect monoclonal components (M-components) include serum and urine protein electrophoresis (PEP), immunofixa-tion electrophoresis, and immunonephelometric methods such as free light chain as-say (sFLC).
Methods: In this study, we retrospectively analyzed 78 patients who were to be tested with FLC without previous evidence of MG in order to investigate the clini-cal meaning of K/L screening. Abnormal K/L in sFLC was found in 25 samples from 21 pa-tients (21/78, 26.92%).
Results: Among them, serum electrophoresis was requested for 16 patients where 5 were diagnosed as either normal or polyclonal gammopathy, 5 as plasma cell myeloma, 5 as monoclonal gammopathy of undetermined significance and 1 as amyloidosis. In total, 11 patients were revealed to have MG related diseases (11/25, 44.0 %).
Conclusions: The clinical function of sFLC as a MG screening tool turned out to be effective based on the result where 16 out of 21 patients who were subject to fur-ther study led to diagnoses of MG related diseases in 11 patients. To provide an ac-curate evaluation for the performance of sFLC as a screening tool for MG, further studies should include additional confirmation of PEP results for patient groups that showed normal K/L ratios.

DOI: 10.7754/Clin.Lab.2012.121113