Fasting plasma caffeine concentration. A guide to the severity of chronic liver disease

Fasting plasma caffeine concentrations (FPCC) were measured in 86 outpatients being examined for suspected or known liver disease. Seven patients (8%) who avoided caffeine consumption had nonmeasurable FPCC; they were dropped from further consideration. The remaining 79 subjects were divided into 4 diagnostic groups: surgical shunt (n = 11); alcoholic, posthepatitic, or primary biliary cirrhosis (n = 29); miscellaneous liver disease (n = 23); and normal liver (n = 16). FPCC was highest (mean, 17.8 mumol/l) in the shunt group, followed by the cirrhosis (12.3), miscellaneous liver diseases (4.6), and normal liver (2.1) groups. FPCC seemed to reflect severity of functional impairment, further supported by highly significant correlations with quantitative liver function tests, such as aminopyrine breath test (Rs = -0.89; n = 66), indocyanine green disappearance (Rs = -0.85; n = 65), and galactose elimination capacity (Rs = -0.70; n = 75). A careful dietary history showed no significant difference in caffeine consumption among the groups. It is suggested that in regular coffee drinkers FPCC might serve as a simple and convenient guide to the severity of functional impairment in chronic liver disease.