EYE-Mobile TRACKer IN the Diagnosis of Minimal Hepatic Encephalopathy

Hepatic encephalopathy (HE) corresponds to the neurological or the neuropsychological symptoms caused by an acute or chronic liver disease and/or porto-systemic shunt. Many patients present neurological symptoms even if their liver disease is stabilized. Furthermore, HE is associated with an altered quality of life and an increased mortality. Its incidence is high with 30 to 80% of cirrhotic patients that will display according to retained diagnostic criteria. HE symptoms are going from subtle neuropsychological abnormalities detected only on neuropsychological testing, minimal HE, to altered consciousness, overt HE. Recently, the therapeutic armamentarium has increased with now several drugs (rifaximine, ammonia lowering agents) that are able to prevent new bouts of HE. Unfortunately, the diagnosis of minimal HE is difficult and no gold-standard is available. None of the proposed test is rapid and easily performed at bedside.

Recently, different studies suggest the potential interest of the study of the ocular movements in HE. Abnormalities in ocular saccads could be an early predictor of cortical impairment. In a pilot feasibility study using an eye-tracker, we could show that cirrhotic patients with minimal HE had, compared to healthy controls, increased latencies, decreased speed of voluntary and reflex saccads, more errors in anti-saccads, more anticipations saccads and more difficulties to fix the target.

Our hypothesis was that the use of the eye-tracker will enable the diagnosis of minimal HE by studying the characteristics of saccads and anti-saccads.

Since no gold-standard is available for the diagnosis of minimal HE, we will use the conclusion of an adjudication committee formed by 2 experts. Their clinical judgment will take into account the results of medical history, clinical examination, neuropsychological testing, PHES, Critical Flicker Frequency test (CFF), ammonemia levels, EEG and brain MRI with spectroscopy.

Gold standard definition: diagnostic of minimal HE as stated by adjudication committee composed of 2 experts. Each patient will be classified as : patient without EH (neither clinical or minimal) and patient with EHM. The results of medical history, clinical examination, EEG results (triphasic waves, decreased frequency), ammonia level (above 50mcmol/L or not), neuropsychological testing encompassing PHES (below -4 or not) and CFF (below 39Hz or not), brain MRI with MR-spectroscopy (HE profile on MRS) will be aggregated to obtain their adjudication. All the tests will be performed by trained personal aware of the evaluation of cirrhotic patients with possible HE. The eye-tracking evaluation will be blinded to the conclusion of the adjudication committee (presence or absence of HE).

Since the data from the eye-tracker are quantitative, a ROC curve will be used to evaluate the diagnostic performance of each parameters measured by the study device (mainly, saccads latencies, voluntary and reflexes ones, and the percentage of errors in saccads, anti-saccads and voluntary anticipations).

The ability of each measure to diagnose minimal HE will be evaluated by the area under the ROC and its 95% confidence interval. Sensibility, specificity, positive and negative predictive values will be given for each possible cut-off with their 95% confidence interval. In order to optimize the diagnostic performance, the most discriminating values will be used to build a multivariate diagnostic model. To prevent overfitting frequently associated with "standard" logistic regression, the selection of variables of interest will be performed with the LASSO method. This method is valuable when the number of subjects are limited.