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Sleep and Rhythms Projects

The Psychomotor Vigilance Task: Role in the Diagnosis of Hepatic Encephalopathy and Relationship with Driving Ability.

Formentin Chiara, De Rui Michele, Zoncapè Mirco, Ceccato Silvia, Zarantonello Lisa, Senzolo Marco, Burra Patrizia, Angeli Paolo, Amodio Piero, Montagnese Sara

Journal of Hepatology

BACKGROUND & AIMS:
Hepatic Encephalopathy (HE) is a syndrome of decreased vigilance, and has been associated with impaired driving ability. The aim of this study was to evaluate the Psychomotor Vigilance Task (PVT), which is used to assess both vigilance and driving ability, in a group of patients with cirrhosis and varying degree of HE.

METHODS:
145 patients (120 males, 59±10 years, MELD 13±5) underwent the PVT; a subgroup of 117 completed a driving questionnaire; a subgroup of 106 underwent the Psychometric Hepatic Encephalopathy Score (PHES) and the electroencephalogram (EEG), based on which, plus a clinical evaluation, they were classed as unimpaired (n=51), minimal (n=35) or mild overt HE (n=20). All were followed up for an average of 13±5 months in relation to the occurrence of accidents/traffic offences, HE-related hospitalizations and death. Sixty-six healthy volunteers evenly distributed by sex, age and education served as reference for the PVT.

RESULTS:
Patients showed worse PVT performance compared to healthy volunteers, and PVT indices significantly correlated with MELD, ammonia levels, PHES and the EEG. Significant associations were observed between neuropsychiatric performance/PVT indices and license/driving status. PVT, PHES and the EEG all predicted HE-related hospitalizations and/or death over the follow-up period; none predicted accidents/traffic offences. However, individuals with the slowest reaction times/most lapses on PVT were often not driving despite having a license. When patients who had stopped driving because of HE-related reasons (n=6) were modeled as having an accident/fine over the subsequent 6/12 months, the PVT was a predictor of accidents/traffic offences, also after correction for MELD and age.

CONCLUSIONS:
the PVT is worthy of further study for purposes of both HE and driving ability assessment.

LAY SUMMARY:
Hepatic Encephalopathy (HE) is a complication of advanced liver disease which can manifests itself as excessive sleepiness. Some patients with HE have been shown to have difficulties driving. Here we use a computer test called Performance Vigilance Task (PVT), which measures sleepiness and has also been used to assess driving competence. We show that PVT performance is fairly stable in healthy individuals, regardless of sex, age and level of education. We also show that PVT performance parallels performance in tests which are commonly used in cirrhotic patients to measure HE. Finally, we observe that PVT indices are worse in patients with cirrhosis who do not drive despite having a license. We therefore suggest that this test may be helpful in quantifying HE and identifying dangerous drivers amongst patients with cirrhosis.

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Interesting debate on our data about driving, vigilance and hepatic encephalopathy!