ARTERIAL AMMONIA WITH BLOOD-AMMONIA-CHECKER-II AND WITH INDOPHENOL REACTION TO ASSESS PRESENCE OF HEPATIC-ENCEPHALOPATHY

Hepatic encephalopathy (HE) is associated with elevated arterial ammon ia levels. The relationship is variable, in part due to ammonia method ology. One method, based on the indophenol reaction (IPh), is interfer ed with a number of amino acids including all aromatic amino acids. We have determined arterial ammonia simultaneously with the Blood Ammoni a Checker II (BAG) as reference method and with the IPh method. The di fference BAC -IPh, mu mol/l, was assumed to express the interference i n the indophenol method (IFI) by amino acids. It may be positive or ne gative. The aim was to establish the value of BAC in comparison with I Ph in the diagnosis of liver disease and overt HE and to assess any ad ded value of IFI. Of two reference groups without disturbances, A (n = 39) had not and B (n = 13) had encephalopathy. Group C consisted of 1 25 liver patients (34 no cirrhosis, 91 cirrhosis) of which 55 had no m anifest HE (C:HE -) and 70 had HE (C:HE+). Median BAC ammonia nitrogen (NH3-N), mu mol/l: A 21, B 35, C 80, C:HE - 57 and C:HE + 98 (A < B < C and A < B < C:HE - < C:HE +, P < 0.001). Median IPh NH3-N, mu mol/l : A 27, B 30, C 30, C:HE-25 and C:HE + 35 mu mol/l (A = B = C and C:HE - < C:HE+, P < 0.01). IFI medians: A -6, B 3, C 40, C:HE-29 and C:HE 58 mu mol/l (A < B (P < 0.05) < C (P < 0.0001); A, B < C:HE - and C:H E+; C:HE < C:HE + (all P < 0.0001)). While BAC correlated weakly with IPh in the (sub)groups C, C:HE -, C:HE + (r = 0.3, 0.3, 0.4, P < 0.05) , it correlated strongly with IFI (r = 0.9, 0.9, 0.8, P < 0.0001). The re was no correlation between IPh and IFI. BAG, as well as IFI, could discriminate all liver patients (C) from both reference groups A and B with 100% positive likelihoods. BAC, IPh and IFI could discriminate b etween HE- and HE+, To differentiate cirrhosis from non-cirrhosis the specificity of IPh was uniformly high and the sensitivity satisfactory , whereas BAC had a high sensitivity but an insufficient: specificity. In conclusion, in blood, BAC is the ammonia determination of choice. It differentiates between reference groups (encephalopathic or not) an d liver disease and the more so HE. The combination of BAC and IPh (in dicating IFI) may eventually be shown useful to rapidly assess the sev erity of underlying liver disease in HE patients. In other biological fluids, IPh is excellent when the inhibiting influence of non-protein nitrogen substances is absent or can be eliminated.