International Journal of Hematology and Oncology 2019, Vol 29, Num 4 Page(s): 143-149
Serum and Urine Free Light Chain Cut-off Detection for a Rational Employment of the Bence- Jones Proteinuria Test in Presence of Monoclonal Gammopathy

Guido D’ANGELO1, Claudio VILLA1, Maria Antonietta ALBERTI1, Isabella SPERDUTI2, Annarita SFERRAZZO1, Silvia VILLA1

1Laboratorio di Chimica-Clinica, Ematologia e Microbiologia Azienda Socio Sanitaria Territoriale (ASST) della Valle Olona Ospedale di Gallarate, Varese, ITALY
2Unità di Biostatistica, Istituto Nazionale Tumori Regina Elena, Roma, ITALY

Keywords: Plasma cell dyscrasia, Monoclonal gammopathy, Serum free light chain, Urine free light chain, Bence-Jones proteinuria
We evaluated whether, in presence of monoclonal gammapathy (MG), serum and urinary free light chains (FLCs) measurement may limit the Bence-Jones proteinuria (BJP) test employement, that is affected by pre-analytical, analytic and post-analytical problems. From March to May 2016, 89 patients who were refered to our laboratory for BJP assay with suspected plasma cell dyscrasia, were evaluated. In presence of MG, it was typified by serum immunofixation electrophoresis. Moreover, sFLC, uFLC and related FLC-κ/λ ratio, as well as glomerular filtration rate (eGFR), were also measured. Patients with MG-κ: the ROC curves analysis showed an accurate comparison between sFLC-κ and sFLC-κ/λ ratio vs BJP-κ positivity detection. The urinary data showed a good correlation between uFLC-κ vs BJP-κ positivity detection, whereas the correlation between uFLC-κ/λ ratio vs BJP-κ positivity detection did not show satisfactory results. Patients with MG-λ: comparing sFLC-λ and sFLC-κ/λ ratio vs BJP-λ positivity detection, the ROC curves analysis showed a good correlation. The urinary data of uFLC-λ vs BJP-λ positivity detection and uFC-κ/λ ratio vs BJP-λ positivity detection did not show satisfactory results for sensitivity and specificity. The absolute values of “k” and “λ” FLC vs BJP positivity detection, statistically are more significant than the FLC-κ/λ ratio. The aggregate data of uFLC, [uFLC-Σ(κ+λ)], identified a statistically significant median value for the detection of BJP positivity. Although the study statistically showed the possibility in same cases to optimize the BJP test employment, further validations to confirm the objectives by us defined are needed.