Dynamic change of serum CA19–9 levels in benign and malignant patients with obstructive jaundice after biliary drainage and new correction formulas

Background CA19–9 is one of the most widely used tumor markers in biliary-pancreatic diseases. The measured value may not factually reflect the genuine CA19–9 level secreted by tumor, which affected by biliary obstruction. There is an urgent need of developing a correction formula of CA19–9 in biliary obstructive patients to guide clinical practice and avoid making improper clinical decision. Methods Clinical characteristics were collected among patients undergoing biliary drainage in our hospital between January 2014 and January 2019. By comparing the malignant and benign patients statistically, dynamic change trend of CA19–9 levels after biliary drainage was obtained. The correction formulas of CA19–9 were generated by means of linear regression. Results 121 patients, including 102 malignant and 19 benign patients, were enrolled in this study. The baseline CA19–9 level of malignant patients is much higher than that of benign patients. Total bilirubin (TB) level was found to be not related with CA19–9 value (p = 0.109). The drop proportion of the average CA19–9 level in the malignant patients (39.2%, IQR -18.4-78.6%) was much lower than that in the benign patients (75.7%, IQR 58.1–86.6%) (p = 0.014). The correction formula, CA19–9True = 0.63 × CA19–9Measured - 20.3 (R2 = 0.693, p<0.001), was generated based on the linear relation between CA19–9 after drainage and CA19–9 before drainage in malignant patients, which had similar diagnostic value with true CA19–9 value. Conclusions Quantitative correction formulas of CA19–9 considering the effect of biliary decompression was first proposed in this study, aiming to provide a more accurate CA19–9 level to make more accurate clinical decision and avoid making improper therapeutic schedule.