Abstract: Objective  To explore the application value of serum cystatin C (Cys-C) and β2-microglobulin (β2-MG) in the diagnosis and short-term efficacy evaluation of multiple myeloma (MM). Methods  A total of 450 patients with MM admitted to Anqing Hospital of Chinese People′s Liberation Army Navy and Jinhua Central Hospital of Zhejiang Province from October 2016 to October 2018 were selected as subjects (MM group), according to the Durie-Salmon staging criteria, including 150 patients in stage Ⅰ, Ⅱ and Ⅲ. A total of 150 healthy subjects were selected as the control group. The levels of Cys-C and β2-MG in the serum of the subjects were determined. The differences of Cys-C and β2-MG levels between the two groups and the MM patients with different Durie-Salmon stages were compared. The differences of Cys-C and β2-MG levels between the patients with different short-term efficacy were compared. The receiver operating characteristic (ROC) curve was used to analyze the value of the two indicators in the evaluation of MM efficacy, and the correlation between Cys-C and β2-GM was analyzed. Logistic regression analysis was used to analyze the multiple factors affecting the clinical efficacy of MM patients. Results  The levels of Cys-C and β2-MG in the serum of the patients with MM were (2.11±0.78) mg/L and (6.07±3.08) g/L respectively, and those in the control group were  (0.75±0.20) mg/L and (1.78±0.59) g/L, with significant differences (t=33.848, P<0.001; t=28.084, P<0.001). The Cys-C levels of Durie-Salmon stage Ⅰ, Ⅱ and Ⅲ patients were (0.99±0.21) mg/L, (1.36±0.17) mg/L and (3.07±1.02) mg/L respectively, and the difference was statistically significant (F=44.157, P<0.001). The β2-MG levels in the serum of patients with stage Ⅰ, Ⅱ and Ⅲ were (2.57±0.75) g/L, (4.66±1.43) g/L, (8.63±2.26) g/L respectively, and the difference was statistically significant (F=57.285, P<0.001). In all the patients, 338 patients were effective, accounting for 75.11%, and 112 patients were ineffective, accounting for 24.89%. The levels of Cys-C and β2-MG in the serum of the  effective MM patients were (1.28±0.23) mg/L and (2.82±0.78) g/L, and those of ineffective patients were (2.97±0.77) mg/L and (6.22±1.92) g/L, with statistically significant differences (t=35.874, P<0.001; t=26.633, P<0.001). The sensitivity of serum Cys-C for predicting short-term efficacy was 83.0%, the specificity was 76.6%, and those of serum β2-MG were 89.3% and 73.6%. The area under curve (AUC) of the serum Cys-C was 0.813 (95%CI: 0.764-0.862), and the AUC of serum β2-MG was 0.865 (95%CI: 0.825-0.906), with a statistically significant difference (Z=2.490, P=0.011). Spearman correlation analysis showed a positive correlation between serum Cys-C and β2-MG (r=0.539, P=0.041). Logistic regression analysis showed that both β2-MG (95%CI: 2.386-5.144, P＜0.001) and Cys-C (95%CI: 2.367-9.702, P＜0.001) were independent factors affecting the short-term efficacy of MM. Multivariate analysis showed that β2-MG (95%CI: 3.549-13.739, P=0.001) was an independent factor affecting the efficacy of MM. Conclusion  The levels of serum Cys-C and β2-M in MM patients are significantly higher than those in healthy people, and they show an increasing trend with the progression of MM disease, which can be used as markers for the pathological staging diagnosis of MM patients. The short-term efficacy of the patients can be evaluated by using the two indicators, and the clinical significance in efficacy evaluation of β2-MG is slightly better than that of Cys-C.

Key words: Multiple myeloma, Diagnosis, Treatment outcome, Cystatin-C, β2-microglobulin