Erythrocyte ammonia in liver disease

This study reports the relevance of plasma and erythrocyte ammonia concentrations in patients with liver disease. Three groups of subjects were studied: group 1, 47 normal subjects; group 2, 73 patients with liver disease; and group 3, 14 patients with portal-systemic encephalopathy (PSE). The difference in plasma ammonia concentrations between groups 1 and 2 was not significant, but for erythrocyte ammonia this was significant (p less than 0.05). Group 3 subjects had significantly elevated plasma (p less than 0.001) and erythrocyte ammonia (p less than 0.001) compared with the other two groups (Mann-Whitney U-test). In group 3, two patients had plasma ammonia values within the reference range, whereas six patients had values within the range of group 2 subjects. However, none of group 3 subjects had erythrocyte ammonia concentrations within the range of either group 1 or 2. A cut-off level of 65 mumol/l was assigned to differentiate group 3 from group 2 subjects. We conclude that erythrocyte ammonia measurement is a better biochemical index of PSE than plasma ammonia.