Critical flicker frequency: diagnostic tool for minimal hepatic encephalopathy.
OBJECTIVE
Minimal hepatic encephalopathy (MHE) is associated with poorer quality of life and increased work disability. Diagnosis requires cumbersome psychometric and neurophysiological tests. We evaluated critical flicker frequency (CFF) to diagnose MHE.


METHODS
156 cirrhotic patients (age 41+/-12.5 yr) without overt encephalopathy (Child A 63, Child B 56, Child C 37) were evaluated by psychometric (number connection tests A, B or figure connection tests A, B), P300 auditory event related potential (ERP) and CFF. MHE was diagnosed by abnormal psychometric and/or P300 auditory event related potential.


RESULTS
Prevalence of MHE was 53% with 27 (43%) in Child's A, 33 (59%) in Child's B and 23 (62%) in Child's C cirrhosis (p=NS). Of 83 patients, 72 (87%) had abnormal psychometry, 64 (77%) had abnormal P300 auditory event related potential (ERP) (380.6+/-28.8 ms) and in 66 (80%) CFF was below 39 Hz. 60 (83%) patients with abnormal psychometry and 51 (80%) with abnormal P300 auditory event related potential had CFF below 39 Hz. CFF sensitivity (96%), specificity (77%) and positive predictive value (68%), negative predictive value (98%) and diagnosis accuracy was 83.3% when compared to patients with both abnormal psychometry and P300ERP.


CONCLUSIONS
Critical flicker frequency is a simple, reliable and accurate test without any age or literacy dependence for the diagnosis of MHE.
Sharma
P
P
Department of Gastroenterology, Room 203, Academic Block, G.B. Pant Hospital, New Delhi 110002, India.
Sharma
B C
BC
Puri
V
V
Sarin
S K
SK
D000328:Adult; D000641:Ammonia / Q000097:blood; D018913:Event-Related Potentials, P300; D005260:Female; D005425:Flicker Fusion; D006501:Hepatic Encephalopathy / Q000175:diagnosis* / Q000209:etiology; D006801:Humans; D008103:Liver Cirrhosis / Q000150:complications*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011594:Psychometrics
D000641:Ammonia