Increased serum levels of quinolinic acid indicate enhanced severity of hepatic dysfunction in patients with liver cirrhosis.

The Model for End-Stage Liver Disease (MELD) score is a tool for assessment of the degree of hepatic insufficiency/failure. Quinolinic acid (QuinA) is a tryptophan metabolite produced by activated macrophages. Here we investigate whether the degree of systemic inflammation (QuinA, neopterin, CRP and IL-6) correlates with clinical liver dysfunction according to the MELD Score. Ninety-four patients with liver cirrhosis were categorized into 2 groups according to baseline MELD score (group I, MELD <20, n = 61, and group II, MELD ≥20, n = 33). Serum levels of QuinA, neopterin, CRP, and IL-6 significantly correlated with MELD score (r = 0.77, 0.75, 0.57, and 0.50; p < 0.0001, respectively). Patients of group II had significantly higher serum levels of QuinA, neopterin, CRP, and IL-6 than group I (p0.0001). ROC curve analysis showed that QuinA and neopterin are more sensitive markers for severity of liver disease than established markers of inflammation such as CRP and IL-6 (sensitivity = 86% and 79%, respectively) (AUC=0.89 and 0.89, respectively). QuinA provided the most sensitive index with regard to the identification of patients with hepatic encephalopathy. Serum levels of QuinA reflect the degree of liver dysfunction. Moreover, high levels of QuinA may serve as a sensitive indicator of hepatic encephalopathy.