Computerized psychometric testing in minimal encephalopathy and modulation by nitrogen challenge and liver transplant

A lack of standardized tests was cited by hepatologists for not testing for minimal hepatic encephalopathy. We therefore compared paper and pencil neuropsychologic tests with a comprehensive computerized assessment (Cognitive Drug Research [CDR], Goring-on-Thames, United Kingdom) of cognitive function.

Eighty-nine cirrhotic patients were studied. Composite scores were calculated from the CDR subtests to reflect 5 cognitive domains, and results were validated by comparison with those from 6 standard paper and pencil tests. Level of impairment was defined using the sum of the standard deviations by which each CDR domain (CDR factor score [CDRS]) and each paper and pencil test score (PHES) differed from age-matched norms. CDRS and PHES were repeated in 21 patients after liver transplantation and CDRS in 24 patients after a 108-g amino acid challenge.

There was a high correlation between the 2 assessment methods (r = 0.748; P = .001). Using multiple regression, Model of End-Stage Liver Disease score (P = .011) correlated with PHES. In contrast, the CDR domains Continuity of Attention and Quality of Episodic Memory were significantly related to venous blood ammonia levels (adjusted R(2) = 0.200; F(6,76) = 4.41; P = .001). There were marked deteriorations in the CDR composite scores representing Accuracy of Working (P = .005) and Episodic Memory (P = .001) after amino acid challenge when blood ammonia increased from 63 +/- 36 to 126 +/- 62 micromol/L (P = .001). Both PHES and CDRS returned to the control range after liver transplantation (PHES: pretransplantation, -6; posttransplantation, 0; P < .001; CDRS: pretransplantation, -6; posttransplantation, -2; P = .003).

CDRS is valuable for the recognition of minimal hepatic encephalopathy.