RÉSUMÉ
OBJECTIVE@#To analyze the effect of serum free light chain (sFLC) on renal function and prognosis in patients with newly diagnosed multiple myeloma (MM).@*METHODS@#The clinical data of 70 newly diagnosed MM patients who received sFLC examination in Fujian Medical University Union Hospital were retrospectively analyzed from April 2012 to November 2016. Univariate analysis was used to analyze the risk factors that associated with renal impairment (RI) and prognosis. Logistic regression and Kaplan-Meier analyze were used to analyze the roles of sFLC in RI and the prognosis.@*RESULTS@#Out of the 70 patients, 20 patients had RI at the initial diagnosis. Compared to normal renal function group, RI group had lower level of hemoglobin, elevated levels of serum uric acid, corrected calcium, serum creatinine, serum β2 microglobulin, and involved sFLC, higher proportion of patients with ISS stage III, involved sFLC≥500 mg/L, hemodialysis (all P＜0.05). Multivariate logistic regression analysis showed that serum uric acid≥430 μmol/L, ISS stage III and a involved sFLC≥500 mg/L were all the independent risk factors for RI in patients with newly diagnosed MM patients (all P＜0.05). Receiver operating characteristic (ROC) curves analysis showed that the involved sFLC was 705.0 mg/L, which was a best cut-off value area under curve (AUC) for prediting RI in patients with MM was 0.727 (P=0.003), sensitivity was 65.0% and specificity was 82.0%). After a median follow-up period of 31 (1-84) months, the median overall survival (OS) of patients with involved sFLC≥500mg/L and involved sFLC＜500 mg/L were 52.0 and 27.0 months, respectively, there was no statistically significant difference (P=0.137). There was also no statistically significant difference in median OS between the high sFLC ratio group (κ/λ＞32 or ＜0.03) and the low sFLC ratio group (0.03≤κ/λ≤32) (27 months vs 40 months, P=0.436).@*CONCLUSION@#The involved sFLC in the RI group is significantly higher than that in the normal renal function group in newly diagnosed MM patients. Serum uric acid≥430 μmol/L, ISS stage III and involved sFLC≥500 mg/L are the independent risk factors for RI. Monitoring sFLC in newly diagnosed MM patients is helpful to the prediction of RI, and the involved sFLC level or sFLC ratio may not affect the prognosis of newly diagnosed MM patients.