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Year : 2018  |  Volume : 7  |  Issue : 2  |  Page : 53-57

Critical flicker frequency: A useful tool in diagnosis of minimal hepatic encephalopathy

Department of Gastroenterology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India

Correspondence Address:
Ajit Kumar
Professor and Head, Department of Medical Gastroenterology, Nizam's Institute of Medical Sciences, Punjagutta, Hyderabad - 500 082, Telangana
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JCSR.JCSR_35_18

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Background: Minimal hepatic encephalopathy (MHE) is viewed as mild neuro-cognitive abnormalities in cirrhotics without overt encephalopathy. Diagnostic strategies for MHE include portosystemic encephalopathy (PSE) syndrome test, critical flicker frequency test (CFF), computerised tests like Inhibitory control test, Scan test etc. We compared critical flicker frequency test with standard PSE syndrome test. Methods: Fifty patients with cirrhotics of liver without overt encephalopathy were studied. PSE syndrome test was done with the standard charts. PSE score was calculated from the normal distribution tables. CFF was tested with manual CFF tool. Results: Their mean age (years) was 46 ± 12.8; there were 45 males. Of these 22, 21 and 7 patients belonged to Child's A, B and C categories. PSE score detected MHE in 40%, of which 35% were in Child's A and 65% in Child's B/C. CFF was normal (>39HZ) in 36% patients and abnormal (<39HZ) in 64% patients. Mean ammonia levels were significantly higher in abnormal CFF (70.87 ± 14.38) as compared normal CFF (32.21 ± 7.9) group (P < 0.001). The sensitivity of CFF for detecting MHE was 85%, specificity 52%, positive predictive value 56% and negative predictive value 85%. Thus, CFF appears to be a good test for excluding MHE. Conclusions: CFF test is highly sensitive (85%) with high negative predictive value (85%). It is a useful test to rule out MHE. The test is simple, quick and in-expensive and can be performed in the outpatient settings.

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