Inhibitory Control Test for the Diagnosis of Minimal Hepatic Encephalopathy

Abstract

Minimal hepatic encephalopathy (MHE) is difficult to diagnose. The Inhibitory Control Test (ICT) measures response inhibition and has diagnosed MHE with 90% sensitivity and specificity in a selected population; high lure and low target rates indicated poor ICT performance. We studied the reliability and validity of ICT for MHE diagnosis. ICT was compared with a psychometric battery (standard psychometric tests [SPT]) for MHE diagnosis and overt hepatic encephalopathy (OHE) prediction. ICT was administered twice for test-retest reliability, before/after transvenous intrahepatic portosystemic shunting (TIPS), and before/after yogurt treatment. The time taken by 2 medical assistants (MA) to administer ICT was recorded and compared with that of a psychologist for cost analysis. One hundred thirty-six cirrhotic patients and 116 age/education-matched controls were studied. ICT (>5 lures) had 88% sensitivity for MHE diagnosis with 0.902 area under the curve for receiver operating characteristic. MHE-positive patients had significantly higher ICT lures (11 vs 4, respectively, P = .0001) and lower targets (92% vs 97%, respectively, P = .0001) compared with MHE-negative patients. The test/retest reliability for ICT lures (n = 50, r = 0.90, P = .0001) was high. ICT and SPT were equivalent in predicting OHE (21%). ICT lures significantly worsened after TIPS (n = 10; 5 vs 9, respectively; P = .02) and improved after yogurt supplementation (n = 18, 10 vs 5, respectively; P = .002). The MAs were successfully trained to administer ICT; the time required for test administration and the associated costs were smaller for ICT than for SPT. ICT is a sensitive, reliable, and valid test for MHE diagnosis that can be administered inexpensively by MAs.