Age-and, education-corrected number connection test and digit symbol test in diagnosis of minimal hepatic encephalopathy

Abstract

To determine the age-and education-corrected control values for the number connection test (NCT) and digit symbol test (DST) psychometric measures to increase their accuracy for diagnosis of minimal hepatic encephalopathy (MHE). The NCT Part A (NCT-A) and DST were administered to 843 healthy volunteers (age range:16-65 years; education:more than 1 year) and 429 patients with liver cirrhosis (with Child-Pugh classification of liver function). The normal values were defined as the mean ± 2 standard deviations (2SD);MHE was defined by abnormal results on at least one psychometric test. The statistical significance of differences in MHE diagnosis according to the various control values (age and education-corrected or not) was assessed by the chi-square test and logistic regression analysis. NCT-A and DST were found to be influenced by age (standard coefficient 0.405, P =0.000 and standard coefficient-0.527, P =0.000 respectively) and education (standard coefficient-0.347, P =0.000 and standard coefficient 0.405, P =0.000 respectively). Among the 120 patients with liver cirrhosis who were diagnosed with MHE (27.97%), 113 had abnormal NCT-A results (26.34%), 54 had abnormal DST results (12.59%),and 47 had abnormal results on both tests (10.96%). Among these 120 MHE-positive patients, 21 were classified as Child-Pugh A (19.81%), 46 as Child-Pugh B (23.71%), and 53 as Child-Pugh C (41.09%);the MHE-positive rate was significantly greater in the patients with Child-Pugh C classification than those with either Child-Pugh B or Child-Pugh A (P < 0.01). Logistic analysis showed that when the control data was corrected for age and education, the MHE diagnosis was related with liver function (P =0.000), regardless of age (P =0.328) and education (P =0.563). When the control data was uncorrected, the MHE diagnosis was not only influenced by liver function (P =0.000) but also by age (P =0.000) and education (P =0.005). Age and education-corrected control values can increase the accuracy of MHE diagnosis by NCT-A and DST.