Critical flicker frequency for diagnosis and assessment of recovery from minimal hepatic encephalopathy in patients with cirrhosis

BACKGROUND: Minimal hepatic encephalopathy (MHE) impairs quality of life and predicts overt hepatic encephalopathy (HE) in cirrhotic patients. Diagnosis of MHE requires cumbersome tests. Lactulose is effective in the treatment of MHE. This study aimed to evaluate the use of critical flicker frequency (CFF) for the diagnosis of MHE in cirrhotic patients after treatment. METHODS: One hundred and ten patients were evaluated by psychometry (number connection tests A, B or figure connection tests A, B), P300 auditory event related potential (P300ERP), venous ammonia, and CFF for MHE. MHE was diagnosed by abnormal psychometry (>2SD age matched controls) and P300ERP. MHE patients were treated with lactulose for one month. Response was defined by normalization (<2SD of matched controls) of both psychometry and P300ERP. RESULTS: Of the 110 patients [Child Turcott Pugh score A: B: C 39: 42: 29, (age 41.6 +/- 11.6 years, M: F 82: 28)], 75 (68%) had abnormal results of psychometric tests, and 74 (67%) had prolonged P300ERP. Fifteen (20%) patients with abnormal results of psychometric tests had normal P300ERP. Thus sixty (54.5%) patients were diagnosed as having MHE. After treatment for one month, 34 (57%) recovered while 26 (43%) continued to have abnormal resents of psychometric or P300ERP tests. CFF was <39 Hz in 72 (65.4%) patients before treatment and in 20 (33.3%) after treatment. CFF sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for the assessment of recovery of MHE were 65%, 91%, 85%, 77% and 80%, respectively. CONCLUSION: CFF is a simple, relatively reliable, and accurate test without any dependence on age or literacy in the diagnosis and assessment of recovery of patients with MHE.