[Prognostic Value and Threshold Effect of Serum C3, C4 in Patients with Multiple Myeloma]

To analyze the prognostic value and threshold effect of serum C3, C4 in patients with multiple myeloma (MM).

The clinical data of 146 patients with MM who visited Suqian First People's Hospital from October 2016 to October 2019 were collected. The patients were divided into deceased group (42 cases) and survival group (104 cases) according to their prognosis and survival. The risk factors affecting the prognosis of the patients were analyzed. The correlation of serum C3 and C4 with prognosis was analyzed by threshold effect. The predictive value of serum C3/C4 on the prognosis of MM patients was evaluated by the receiver operating characteristic (ROC) curve. Nomogram model was constructed, and the discrimination and accuracy of the model were evaluated. The nomogram model was internally validated by bootstrap resampling.

Durie-Salmon (DS) stage Ⅲ, decreased low density lipoprotein cholesterol (LDL-C) and apolipoprotein B (Apo B), elevated homocysteine (Hcy), uric acid (UA), and serum C3 and C4 were independent risk factors affecting the prognosis of MM patients (P < 0.05). Curve fitting showed that the mortality probability of MM patients increased with the increase of serum C3 and C4 levels. The threshold effect analysis showed that when serum C3 was higher than 1.2 g/L or serum C4 was higher than 0.37 g/L, the mortality rate of MM patients increased with the increase of the index levels; When serum C3 was lower than 1.2 g/L or serum C4 was lower than 0.37 g/L, the mortality rate of MM patients had no significant correlation with the indexes. Serum C3 and C4 had a good predictive value for the prognosis of MM patients, and the combination of C3 and C4 had a higher predictive value. The validation results showed that the nomogram model constructed in our study had good discrimination and high accuracy.

Elevated levels of serum C3 and C4 are independent risk factors for mortality in patients with MM. The combination of serum C3 and C4 is more valuable in predicting mortality in MM patients than C3 or C4 alone, which can be used as a sensitive index to evaluate the prognosis of MM patients.