ObjectiveTo research the association between the prognostic nutritional index (PNI) and the prognosis of patients with malignant obstructive jaundice (MOJ) after interventional treatment. MethodsThe clinicopathologic data of patients with MOJ who were clinically diagnosed and underwent interventional treatment in the Affiliated Hospital of Southwest Medical University, from September 2018 to June 2021, were gathered retrospectively. The X-Tile statistical software was used to determine the optimal critical value of PNI before treatment, then the patients were allocated into the high PNI group (PNI was the optimal critical value or more) and low PNI group (PNI was less than the optimal critical value). The clinicopathologic characteristics of the two groups were compared. The Kaplan-Meier method was used to draw survival curve for survival analysis, and the Cox proportional hazards regression model was used to analyze the risk factors affecting the prognosis of patients with MOJ (the prognostic index was overall survival). ResultsA total of 205 patients were included in this study. The optimal critical value of PNI was 37.5. There were 154 cases in the high PNI group and 51 cases in the low PNI group, respectively. The proportions of the patients with biliary infection, CA19-9 ≥400 kU/L, hemoglobin <120 g/L, albumin <30 g/L, total bilirubin ≥300 μmol/L, and alanine aminotransferase <300 U/L were higher in the low PNI group as compared with the high PNI group (P<0.05). The median overall survival of patients in the high PNI group and low PNI group was 7.1 months and 3.6 months, respectively. The overall survival curve of the former was better than that the latter (χ2=18.514, P<0.001). The median follow-up time of 205 patients was 6.2 months, with a median overall survival of 5.3 months. The multivariate results of Cox proportional hazards regression model analysis showed that the probability of overall survival lengthening was increased for the patients with more times of PTCD, with stent implantation, with treatment for primary tumor, without metastasis, and with preoperative PNI ≥37.5 (P<0.05). ConclusionFrom the results of this study, preoperative peripheral blood PNI has a certain association with the prognosis of patients with MOJ after interventional treatment, and it is expected to be used to predict the prognosis of patients with MOJ in the future.