Subclinical hepatic encephalopathy (SHE) is currently diagnosed by psychometric tests or neurophysiologic techniques. In view of its sociomedical relevance, simple and reproducible tests for routine diagnosis are required. This study evaluates critical flicker-frequency thresholds for quantification of low-grade hepatic encephalopathy. A total of 115 patients (92 with cirrhosis, 23 controls) were analyzed for HE severity (mental state, computerized psychometric tests), and the threshold frequencies at which light pulses are perceived as fused (fusion frequency) or flickering light (critical flicker frequency [CFF]). CFF was a highly reproducible parameter with little age, day-time, and training dependency. CFFs in cirrhotic patients without HE (HE 0) were not different from those found in noncirrhotic controls. Significantly lower CFFs were found in cirrhotic patients with subclinical or manifest HE, and the various HE groups separated from each other at a high level of significance (P < .01). By using a CFF cut-off value of 39 Hz, a 100% separation of patients with manifest HE from noncirrhotic controls and HE 0 cirrhotic patients was obtained. SHE patients separated from HE 0 cirrhotic patients with high sensitivity (55%) and specificity (100%). The HE severity-dependent differences were found in both, alcoholic and posthepatitic cirrhosis. Statistically significant correlations (P < .01) were found between CFFs and individual psychometric tests. Aggravation of preexisting HE after transjugular intrahepatic portosystemic stent shunt (TIPS) implantation was accompanied by a corresponding decrease of CFF, whereas improvement of HE increased CFF. In conclusion, CFF is a sensitive, simple, and reliable parameter for quantification of low-grade HE severity in cirrhotic patients and may be useful for the detection and monitoring of SHE. H epatic encephalopathy (HE) is a frequent complication of cirrhosis and its appearance indicates poor prognosis. 1-4 HE is usually classified into 4 stages according to the presence and severity of neuropsychiatric symptoms on clinical evaluation. 5 However, a significant proportion of cirrhotic patients, who appear normal on clinical examination, exhibit various quantifiable neuropsychologic deficits and this condition has been termed subclinical hepatic encephalopathy (SHE). 6-10 Whereas detection of overt HE (grade I-IV) is made clinically and does not provide a major diagnostic challenge, diagnosis of SHE is problematic. Psychometric and electrophysiologic tests are currently used for detection of SHE. In addition, proton-magnetic resonance spectroscopy of the brain may bear a not yet fully elaborated diagnostic potential, 11 but is unsuitable for clinical routine. Electrophysiologic tests such as visual-evoked, somatosensory-evoked, or brain stem auditory-evoked potentials suffer from methodologic problems, require sophisticated equipment and analysis, and exhibit a lower sensitivity than psychometric tests. 7,12-14 Psychometric bedside tests, such as the number-connection test...
