Development and validation of a risk score for predicting clinical success after endobiliary stenting for malignant biliary obstruction

Background Endoscopic drainage is the primary treatment for unresectable malignant biliary obstruction (MBO). This study developed and validated a pre-endoscopic predictive score for clinical success after stent placement. Methods Patients with unresectable MBO undergoing ERCP-guided endobiliary stent placement between 2007 and 2017 were randomly divided into derivation (n = 383) and validation (n = 128) cohorts. To develop the risk score, clinical parameters were built by logistic regression to predict (1) ≥ 50% total bilirubin (TB) resolution within 2 weeks and (2) bilirubin normalization (TB level <1.2 mg/dL) within 6 weeks following stenting. The scoring scheme was applied to the validation cohort to test its performance. Results A ≥ 50% TB resolution within 2 weeks was shown in 70.5% of cases. The risk scoring scheme had areas under the receiver operating characteristic curve (AUROC) of 0.70 (95% CI, 0.64–0.76) and 0.67 (95% CI, 0.57–0.77) in the derivation and validation cohorts, respectively. Thirty-one percent had TB normalization within 6 weeks after stenting. Significant predictors for TB normalization were extrahepatic biliary obstruction (odds ratio [OR] = 2.35), pre-endoscopic TB level (OR = 0.88), and stent type (OR = 0.42). The AUROC of a risk score for predicting TB normalization within 6 weeks was 0.78 (95% CI, 0.72–0.83) and 0.76 (95% CI, 0.67–0.86) in the derivation and validation cohorts, respectively. A score > 1.30 yielded a specificity of 98% and a positive predictive value of 84% for predicting TB normalization. A score of < -4.18 provided a sensitivity of 80%–90% and a negative predictive value of 90%–93% for predicting the absence of TB normalization. Conclusions The pre-endoscopic scoring system comprising biliary obstruction level, liver biochemistry, and type of stent provides prediction indices for TB normalization within 6 weeks after stenting. This scheme may help endoscopists identify patients with unresectable MBO suited for palliative stenting.