目的 探讨多发性骨髓瘤（MM）患者免疫状态及检测外周血红细胞分布宽度标准差（RDW-SD）、血清游离轻链κ/λ比值（sFLCR）、可溶性B细胞成熟抗原（sBCMA）水平变化与预后的关系，为该病的病情判断和预后评估提供参考。 方法 选取医院2019年7月至2021年7月收治的MM患者182例作为观察组，所选患者均随访3年，随访期间失访6例，最终纳入176例进行研究，将最终纳入的176例患者根据预后情况分为预后不良组（53例）和预后良好组（123例），另外随机选取于我院同期接受健康体检的健康志愿者50名作为对照组。比较观察组和对照组免疫状态，分析MM患者预后不良的单因素，予以Cox回归分析MM患者预后不良的危险因素，将预后良好组纳入阴性，预后不良组纳入阳性，绘制受试者工作特征曲线（ROC）分析外周血RDW-SD、血清sFLCR、sBCMA单独及联合检测对MM患者预后不良的预测价值，获取曲线下面积（AUC），最佳截断值的确定依据约登指数最大的原则，联合检测的预测价值分析通过拟合方程进行。 结果 观察组外周血辅助性T细胞17（Th17）、血小板/淋巴细胞比值（PLR）水平高于对照组（P < 0.05），外周血调节性T细胞（Treg）水平低于对照组（P < 0.05）。预后不良组外周血RDW-SD及血清sBCMA水平高于预后良好组（P < 0.05），血清sFLCR水平低于预后良好组（P < 0.05）。Cox回归分析显示，外周血RDW-SD水平（HR = 1.091，95%CI：1.027 ~ 1.159）、血清sFLCR水平（HR = 1.095，95%CI：1.035 ~ 1.159）、血清sBCMA水平（HR = 1.088，95%CI：1.016 ~ 1.165）均是MM患者预后不良的独立危险因素（P < 0.05）。ROC分析显示，外周血RDW-SD、血清sFLCR、sBCMA联合检测预测MM患者预后不良的AUC值为0.880，高于三者单一检测（0.805、0.786、0.780，P < 0.05），敏感度、特异度分别为94.34%、68.29%。 结论 MM患者存在免疫状态异常现象，且患者发生预后不良与外周血RDW-SD及血清sBCMA水平和血清sFLCR水平有关，外周血RDW-SD、血清sFLCR、sBCMA联合检测预测MM患者预后不良更具优势。

Objective To explore the correlation between the immune status of patients with multiple myeloma （MM） and the dynamic changes in peripheral blood red blood cell distribution width standard deviation （RDW-SD）， serum free light-chain κ/λ ratio （sFLCR）， and soluble B-cell maturation antigen （sBCMA）， as well as their implications for prognosis. This study aims to provide a reference for evaluating disease progression and assessing patient outcomes. Methods 182 MM patients admitted to the hospital between July 2019 and July 2021 were enrolled as the study group. All selected patients were followed up for 3 years， with 6 cases lost to follow-up， resulting in a final cohort of 176 patients. These patients were further divided into two groups based on their prognosis： the poor-prognosis group （53 cases） and the good-prognosis group （123 cases）. Additionally， 50 healthy volunteers who underwent health check-ups during the same period were randomly selected as the control group. The immune status of both the study group and the control group was compared. Univariate analysis was conducted to identify factors associated with poor prognosis in MM patients， and Cox regression analysis was performed to determine risk factors for poor prognosis. The good-prognosis group was designated as the negative group， while the poor-prognosis group was designated as the positive group. The predictive value of peripheral blood RDW-SD， serum sFLCR， and sBCMA-both individually and in combination-for poor prognosis in MM patients was evaluated by constructing receiver operating characteristic （ROC） curves. The area under the curve （AUC） was calculated， and the optimal cut-off value was determined using the Youden index. Finally， the predictive value of the combined test was analyzed by fitting an appropriate equation. Results Levels of peripheral blood Th17 cells and platelet-to-lymphocyte ratio （PLR） were significantly higher in the study group compared to the control group （P < 0.05）， while the level of peripheral blood regulatory T cells （Tregs） was significantly lower than that in the control group （P < 0.05）. Additionally， levels of peripheral blood RDW-SD and serum sBCMA were significantly higher in the poor prognosis group compared to the good prognosis group （P < 0.05）， whereas the serum level of sFLCR was significantly lower than that in the good prognosis group （P < 0.05）. Cox regression analysis revealed that elevated peripheral blood RDW-SD （HR = 1.091， 95%CI： 1.027 ~ 1.159）， reduced serum sFLCR （HR = 1.095， 95%CI： 1.035 ~ 1.159）， and increased serum sBCMA （HR = 1.095， 95% CI： 1.016 ~ 1.165） were independent risk factors for poor prognosis in patients with MM （P < 0.05）. ROC curve analysis demonstrated that the combination of peripheral blood RDW-SD， serum sFLCR， and sBCMA assays achieved an AUC value of 0.880 for predicting poor prognosis in MM patients， which was significantly higher than those of the three individual assays （AUC values： 0.805， 0.786， 0.780； P < 0.05）. The sensitivity and specificity of this combined assay were 94.34% and 68.29%， respectively. Conclusions MM patients exhibited abnormal immune status and poor prognosis， which was associated with elevated levels of peripheral blood RDW-SD and serum sBCMA， as well as reduced serum sFLCR. Moreover， the combination of peripheral blood RDW-SD， serum sFLCR， and sBCMA demonstrated superior predictive value for poor prognosis in MM patients.