31 13C-AMIN0PYRINE AND 13C-PHENYLALANINE BREATH TESTS AS A DYNAMIC MEASURE OF LIVER FUNCTION IN CHILDREN

Abstract

Dynamic liver function tests like the MEGX test and the 13C-aminopyrine breath test (13C-AP-BT) have been developed to provide a quantitative assessment of microsomal function. In chronic liver diseases the activity of phenylalanine hydroxylase is reduced. The aim of the present study was to compare the results of the 13C-phenylalanine breath test (13C-Phe-BT) with well established liver function tests (13C-AP, MEGX) and routine laboratory data. In 17 patients (age: 5 months to 17 years) with chronic hepatic diseases 13C-AP and 13C-Phe breath tests were performed. After oral administration ot 2 mg/kg bw 13C-AP and 1.5 mg/kg bw 13C-Phe, resp., the 13CO2-exhalation was analysed using mass spectrometry and expressed as cumulative 13C-elimination rate (13C-E). in 14 of the patients the MEGX test was performed (1 mg/kg bw Lidocain i.v.). The results of these dynamic liver function tests were compared to amino transferases, GGT, PCHE, PTT, albumin, bilirubin and bile acids. The range of 13C-E was 0 to 18.6 % for 13C-AP (normal: > 9.2 %) and 0 to 14.3 % for 13C-Phe (normal: > 10.8 %), resp.. 13C-E of AP and Phe was significantly correlated (r=0.65; p< 0,01), although distinct differences were seen intraindividually. Only 13C-E-AP was correlated with the MEGX test (r=0.55; p<0.05). The results of both breath tests correlated with the PTT (r=0.62 and 0.72, resp.; p<0.01). However, no correlation was found between the 13C-E of both tests and the activities of amino transferases, GGT, PCHE, and the concentrations of bile acids, albumin, and bilirubin.These preliminary results show a good correlation between the 13C-AP breath test and the MEGX test, both reflecting microsomal liver function. Reduced 13C-E-Phe indicates diminished activity of phenylalanine hydroxylase in liver diseases. However, marked intraindividual differences in the results of the breath tests were noted. Their prognostic significance has to be evaluated.