Diagnostic Value Of Ascitic Fluid Total Protein In Differential Diagnosis Of Ascites:A Prospective Multicenter Study

Background and aims: Diagnostic performance of ascitic fluid total protein(AFTP)concentration remained unsettled.American Association for the Study of Liver Diseases(AASLD)did not recommend it for clinical use.As a routine biochemical test for ascites at home and abroad,this study aims to explore its role in the differentiation of different types of ascites.Methods: 704 consecutive patients with new-onset ascites were prospectively enrolled in this study,506 cases were admitted to Wuhan Union Hospital from May 2015 to March 2017 as training group,and other 198 cases were admitted to Wuhan Union Hospital,Tongji Hospital and Central South Hospital from April 2017 to October 2017 as validation group.By studying the role of AFTP in differentiating different types of ascites,and comparing with Rivalta test,SAAG,to explore its clinical application value.Results: In the training cohort,when ascites was in the classification of exudatetransudate,Rivalta test had a sensitivity of 85%,specificity of 71%,negative predictive value(NPV)of 82%,positive predictive value(PPV)of 76%,diagnostic accuracy of 79%;while at a predetermined cut-off value of 25 g/L,quantitative AFTP assay had a sensitivity of 86%,specificity of 84%,NPV of 84%,PPV of 86%,diagnostic accuracy of 85%;the AUC(area under curve)of the ROC(receiver operating characteristic)is 0.935.Simultaneously according to the differentiation of non-portal hypertension(nonPH)from portal hypertension(PH),quantitative AFTP assay had a sensitivity of 90%,specificity of 84%,NPV of 89%,PPV of 84%,diagnostic accuracy of 87%,the AUC of the ROC is 0.958.In the whole cohort,when differentiating non-PH from PH,AFTP had a sensitivity of 90%,specificity of 85%,NPV of 90%,PPV of 84%,diagnostic accuracy of 87%;Compared with the diagnostic performance of clinical gold standard SAAG,which had a sensitivity of 80%,specificity of 96%,NPV of 85%,PPV of 95%,diagnostic accuracy of 89%.All these indicated higher sensitivity for SAAG in detecting portal hypertensive ascites and higher sensitivity for AFTP in detecting nonportal hypertensive ascites.AFTP ?25.0 g/L was observed in 92% of malignant ascites and 98% of tuberculous peritonitis,while the corresponding SAAG<11g/L ratio is 75% and 93% respectively.In the patients misdiagnosed according to SAAG classification,the diagnostic accuracy of AFTP was 54%,of which 75%(3/4)tuberculous ascites and 68%(27/40)malignant ascites that misdiagnosed were corrected by AFTP.In mixed ascites,quantitative AFTP assay could be used to identify peritoneal lesions(such as peritoneal metastasis of malignant tumors,peritoneal changes of non-portal benign ascites such as tuberculous peritonitis,etc.),AFTP of 78%(42/54)without peritoneal changes were less than 25g/L,73%(16/22)with peritoneal changes had a high AFTP(?25g / L);and regardless of the presence of peritoneal changes,most mixed ascites had a SAAG that more than 11 g / L.Conclusions: For the differential diagnosis of different types of ascites,quantitative AFTP assay is superior to Rivalta test,the differentiation of non-PH from PH is superior to traditional exudate-transudate classification,quantitative AFTP assay has excellent diagnostic performance in non-PH-related ascites and the mixed ascites with peritoneal changes,and quantitative AFTP assay has a certain corrective effect on misdiagnosed cases according to SAAG classification.Thus,it should be clinically popularized and determined in diagnostic workup of the patients with ascites.