Role of CA 19-9 and its Ratio with CRP and Total Bilirubin in Differentiating Malignant from Benign Obstructive Jaundice

Abstract

Introduction: Obstructive Jaundice resulting from various benign and malignant conditions of gastrointestinal tract may lead to variable increase in serum Carbohydrate Antigen (CA19-9), C Reactive Protein (CRP) and serum bilirubin level. Aim: To investigate the diagnostic utility of CA19-9, CRP, serum bilirubin level and their ratios, CA19-9/total bilirubin ratio and CA19-9/CRP, ratio in differentiating malignant obstructive jaundice from benign obstructive jaundice. Materials and Methods: This case control study considered 75 diagnosed cases of obstructive jaundice which were further divided into two sub-categories; Group I consisted of 36 patients with malignant obstructive jaundice and Group II consisted of 39 patients with benign obstructive jaundice. All patients were subjected to laboratory investigations which included CA 19-9, CRP and Total bilirubin. Median and interquartile range was used in descriptive statistics, as the data was not following normal distribution. The different groups were analysed using non parametric test and ROC used for predictive analysis. The results were statistically analysed using statistical software, R version 3.4.0. Results: A significant increase in serum CA 19-9, serum bilirubin and CRP was observed in malignant obstructive jaundice compared to benign obstructive jaundice. As per ROC analysis CA19-9 alone has the highest sensitivity value of 91.67, at a cut-off point of 410 U/mL whereas CRP reported the lowest in both sensitivity and specificity. However, when a ratio of CRP i.e., (CA19-9/CRP) is taken, the sensitivity value of 83.33 is obtained at a cut-off point of 40.56 and area under ROC is also significant, but there is decrease in both sensitivity and specificity when the ratio of bilirubin i.e., CA19-9/Bilirubin is considered. A logistic regression analysis found total bilirubin to be the most significant independent factor having an impact on malignancy. Conclusion: CA19-9, at a cut-off value of 410, has better sensitivity in differentiating malignant from benign obstructive jaundice compared to the ratio with CRP and total bilirubin. One of the major finding of the study is when CRP is adjusted for CA 19-9 i.e., CA19-9/CRP ratio proves to be a better marker, that can be used along with CA 19-9 in differentiating between malignant and benign obstructive jaundice.

Keywords

• carbohydrate antigen (ca19-9)
• c reactive protein (crp)
• malignant obstructive jaundice
• total bilirubin