Evaluating the screening value of serum light chain ratio, β(2) microglobulin, lactic dehydrogenase and immunoglobulin in patients with multiple myeloma using ROC curves

OBJECTIVE: Several laboratory and imaging assays are required to diagnose multiple myeloma (MM). Serum and urine immunofixation electrophoresis are two key assays to diagnose MM, while they have not been extensively utilized in Chinese hospitals. Serum light chain (sLC), β(2) microglobulin (β(2)-MG), lactic dehydrogenase (LDH), and immunoglobulin (Ig) are routinely measured in the majority of Chinese hospitals. Imbalance of sLC ratio (involved light chain/uninvolved light chain) is frequently observed in MM patients. This study aimed to evaluate the screening value of sLC ratio, β(2)-MG, LDH, and Ig in MM patients using receiver operating characteristic (ROC) curves. METHODS: Data of 303 suspected MM patients, who were admitted to the Taizhou Central Hospital between March 2015 and July 2021, were retrospectively analyzed. In total, 69 patients (MM arm) met the International Myeloma Working Group (IMWG) updated criteria for the diagnosis of MM, while 234 patients were non-MM (non-MM arm). All patients’ sLC, β(2)-MG, LDH, and Ig were measured using commercially available kits according to the manufacturer’s instructions. The ROC curve analysis was employed to assess the screening value of sLC ratio, β(2)-MG, LDH, creatinine (Cr) and Ig. The statistical analysis was carried out by SPSS 26.0 (IBM, Armonk, NY, USA) and MedCalc 19.0.4 (Ostend, Belgium) software. RESULTS: There was no significant difference between the MM and non-MM arms in terms of gender, age and Cr. The median sLC ratio in the MM arm was 11.5333, which was significantly higher than that of 1.9293 in the non-MM arm (P<0.001). The area under the curve (AUC) of sLC ratio was 0.875, which indicated a robust screening value. The optimal sensitivity and specificity were 81.16% and 94.87% respectively, when the sLC ratio was set as 3.2121. The serum levels of β(2)-MG and Ig were higher in the MM arm than those in the non-MM arm (P<0.001). The AUC values of β(2)-MG, LDH, and Ig were 0.843 (P<0.001), 0.547 (P = 0.2627), and 0.723 (P<0.001), respectively. The optimal cutoff values of β(2)-MG, LDH, and Ig were 1.95 mg/L, 220 U/L, and 46.4 g/L respectively, in the context of screening value. The triple combination of sLC ratio (3.2121), β(2)-MG (1.95 mg/L), and Ig (46.4 g/L) yielded a higher screening value compared with that of sLC ratio alone (AUC, 0.952; P<0.0001). The triple combination had a sensitivity of 94.20% and a specificity of 86.75%. The addition of LDH to the triple combination and formation of quadruple combination did not optimize the screening value, with AUC, sensitivity, and specificity of 0.952, 94.20%, and 85.47%, respectively. CONCLUSION: The triple combination strategy (sLC ratio, 3.2121; β(2)-MG, 1.95 mg/L; Ig, 46.4 g/L) is accompanied by remarkable sensitivity and specificity for screening MM in Chinese hospitals.