To evaluate the clinical value of serum levels of lactate dehydrogenase (LDH), interleukin-6 (IL-6), procalcitonin (PCT) and high-sensitivity C-reactive protein (hs-CRP) on the prognosis of patients with multiple myeloma (MM) complicated with infection.

The clinical data of 141 patients with MM admitted to Cangzhou Integrated Traditional Chinese and Western Medicine Hospital from June 2019 to June 2022 were analyzed, retrospectively. According to the incidence of infection, patients with MM were divided into infection group (84 cases) and control group (57 cases). Differences of serum LDH, IL-6, PCT and hs-CRP levels between the two groups, and the changes of LDH, IL-6, PCT and hs-CRP levels before and after treatment in infection group were compared, respectively. Also, the levels of IL-6, PCT, LDH and hs-CRP of patients with different clinical outcomes (recovery, persistent infection, septic shock and septic death) in infection group were compared. The influence of LDH, IL-6, PCT and hs-CRP levels on the prognosis of MM patients with infection were analyzed by Multivariate Logistic regression analysis, and the predictive value of serum LDH, IL-6, PCT and hs-CRP levels on the prognosis of MM patients with infection were evaluated by the receiver operating characteristic curve (ROC).

The serum levels of LDH, IL-6, PCT and hs-CRP in infection group were significantly higher than those of the control group (U = 67.491, 38.425, 53.597, 29.617, all P < 0.001). Compared with before treatment, the levels of LDH, IL-6, PCT and hs-CRP of patients in infection group reduced significantly after treatment (t = 10.150, 15.012, 12.062, 16.756, all P < 0.001). There were statistically significant differences in serum LDH, IL-6, PCT and hs-CRP levels before treatment among patients with different prognosis in infection group (all P < 0.001); the levels of serum LDH, IL-6, PCT and hs-CRP of patients with persistent infection, septic shock, and septic death before treatment were significantly higher than those in the recovery period, which were significantly higher in patients with septic death than those with persistent infection and septic shock (all P < 0.05). Multivariate Logistic regression analysis showed that the increase of LDH (OR = 5.436, 95%CI: 1.864-15.850, P = 0.002), IL-6 (OR = 4.572, 95%CI: 1.470-14.223, P = 0.009), PCT (OR = 4.797, 95%CI: 1.738-13.240, P = 0.002), hs-CRP (OR = 5.089, 95%CI: 1.794-14.436, P = 0.002) were independent risk factors for the prognosis of MM with bacterial infection. The ROC analysis showed that the areas under ROC (AUCs) of serum LDH (the best threshold: 853.00 U/L) (sensitivity and specificity were 73.41% and 61.78%), IL-6 (the best threshold: 21.50 pg/ml) (sensitivity and specificity were 65.24% and 52.31%), PCT (the best threshold: 9.90 pg/ml) (sensitivity and specificity were 68.98% and 46.37%) and hs-CRP (the best threshold: 35.3 mg/L) (sensitivity and specificity were 59.49% and 45.34%) in the diagnosis of MM with bacterial infection were 0.813, 0.849, 0.858 and 0.805, the AUC of combined diagnosis of the four indexes was 0.884 (sensitivity and specificity were 91.32% and 94.16%), which were significantly higher than the AUCs of the four single indexes, respectively (all P < 0.001).

Combination of serum LDH, IL-6, PCT and hs-CRP levels for the diagnosis of MM with bacterial infection has a high prognosis value, which can be used as an indicator for monitoring clinical efficacy and evaluating clinical prognosis.