Critical flicker frequency and continuous reaction

Authors: Mette Munk Lauridsen Peter Jepsen Hendrik Vilstrup

Publish Date: 2011/04/12

Volume: 26, Issue: 2, Pages: 135-

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Abstract

Minimal hepatic encephalopathy MHE is intermittently present in up to 2/3 of patients with chronic liver disease It impairs their daily living and can be treated However there is no consensus on diagnostic criteria except that psychometric methods are required We compared two easytoperform reproducible bedside methods the critical flicker frequency CFF and continuous reaction times CRT tests A CFF 39 Hz and CRTindex 19 index the ratio 50/90 minus 10 percentiles of reaction times indicates cerebral dysfunction 154 patients with acute or chronic liver disease with out overt hepatic encephalopathy HE underwent both tests at the same occasion Both tests were abnormal in 20 of the patients and both tests were normal in 40 of the patients In more than 1/3 the two tests were not in agreement as CFF classified 32 and CRTindex classified 48 of the patients as having MHE p  0005 The two tests were weakly linearly correlated r2 = 014 p  0001 and neither test correlated with the metabolic liver function measured by the Galactose Elimination Capacity GEC nor with the blood ammonia concentration Both tests identified a large fraction of the patients as having MHE and cleared only 40 The two tests did not show concordant results likely because they describe different aspects of MHE the CFF gives a measure of astrocytic metabolic state and hence pathogenic aspects of MHE whereas the CRT measures a composite key performance viz the ability of reacting appropriately to a sensory stimulus The choice of test depends on the information needed in the clinical and scientific care and study of the patients

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