Caffeine clearance test: a quantitative liver function assessment in patients with liver cirrhosis

Quantitative assessment of live function is an important work-up for patients with liver cirrhosis. The aim of the present study was to clarify the role of caffeine clearance test in the quantitative measurement of metabolizing capacity of the liver.

Twenty-eight patients with liver cirrhosis and 28 normal healthy volunteers were enrolled in this study. After an overnight fast, the first blood sample was collected at 8 a.m., immediately followed by an oral administration of 150 mg caffeine. Subsequent samples of venous blood were obtained at 8.30 a.m., 9 a.m., 11 a.m., 2 p.m. and 5 p.m. The caffeine clearance was determined using two caffeine concentrations from blood samples taken at 2 p.m. and 5 p.m., which were then measured by an enzyme multiple immunoassay technique.

The serum caffeine clearance was significantly higher in the control group than in the patient group (1.72 +/- 1.06 vs. 0.78 +/- 0.77 ml/min/kg, p < 0.0001). Elimination half-life was significantly prolonged in the patient group (3.74 +/- 1.05 vs. 2.69 +/- 0.75 hours, p < 0.0001). The influence of cigarette smoking was also evident: higher clearance and shorter half-life of caffeine were noted in the smoking subjects. In the non-smokers, caffeine clearance was 1.30 +/- 0.90 and 0.51 +/- 0.47 ml/min/kg and half-life of caffeine was 2.89 +/- 0.78 and 4.06 +/- 0.93 hours, respectively (control vs. patient, p < 0.05). In the smokers, caffeine clearance was 2.30 +/- 0.98 and 1.13 +/- 0.96 ml/min/kg and half-life of caffeine was 2.41 +/- 0.63 vs. 3.31 +/- 1.06 hours, respectively (control vs. patient, p < 0.05). During the mean six-month period of follow-up, the mortality rate was significantly higher in those patients with caffeine clearance less than 0.5 ml/min/kg than in those with clearance more than 0.5 ml/min/kg (46.1% vs. 6.7%, p < 0.05). A significantly negative correlation between the serum caffeine clearance and the Child-Pugh's score was also demonstrated (r = -0.851, p < 0.0001).

Serum caffeine clearance determined at two points of blood concentration is a useful method to evaluate the severity of liver disease and predict short-term survival of cirrhotic patients. It offers another choice for the quantitative measurement of liver functional reservoir.