Covert/Minimal Hepatic Encephalopathy

Hepatic encephalopathy (HE) is often graded based on severity. Covert or minimal hepatic encephalopathy (C/MHE) is subtle, often without readily apparent clinical signs and therefore difficult to detect. Nevertheless, C/MHE has been associated with an increased risk of falls and motor vehicle accidents, worsened liver-related outcomes from cirrhosis, and decreased quality of life

C/MHE appears to be common—though almost certainly underdiagnosed—in patients with cirrhosis. In a recent systematic review of 101 studies, researchers pooled data from 16,000 patients with cirrhosis to estimate the prevalence of C/MHE and identify patient characteristics associated with excess risk. In all studies, C/MHE was most often diagnosed using the psychometric hepatic encephalopathy score (PHES), a composite of five separate psychometric tests.

Key study findings:

  • The prevalence of C/MHE increased with worsening liver disease: 29%, 46%, and 62% for Child-Pugh class A, B, and C, respectively.
  • C/MHE was most common in patients with cirrhosis due to alcohol (46%) or viral hepatitis (41%) and least common in patients with cirrhosis due to metabolic dysfunction–associated steatotic liver disease (35%) or autoimmune liver disease (27%).
  • Lab markers of cirrhosis severity (i.e., elevated serum ammonia, bilirubin, and INR, and low serum albumin, Hgb, and platelets) were associated with C/MHE, but none are highly accurate predictors.

Unfortunately, the PHES is tedious to use in a primary care setting (and under copyright, limiting its accessibility); however, the number connection test (NCT), one of the five psychometric tests that constitute the PHES, is easily administered and has a sensitivity of 77% for C/MHE.

NCT instructions: 

  • Step 1: Make sure the patient is alert enough to cooperate for this test, can see adequately, has a writing surface, is able to count, and can hold a pen or pencil.
  • Step 2: Inform the patient that you will be timing the test and to complete the number connections from 1 to 25 as fast as the patient can without lifting the pen or pencil from the paper.
  • Step 3: If an error occurs, point it out immediately and allow the patient to correct the error. The total elapsed time to complete the test, including the time spent correcting errors, is the score.
  • Step 4: Record the time spent to complete the test.
    • Patients without HE should finish the test in a number of seconds less than or equal to their age in years. In other words, if a patient is 50 years old, they should be able to finish the test in under 50 seconds.

Another reasonable screening approach is the SIP-CHE, consisting of the four yes-or-no statements below. A score >0 at baseline predicts C/MHE with a sensitivity of 80%. 

  • I do not maintain balance.
  • I act irritable or impatient with myself. 
  • I am not doing any of my usual physical recreation or activities.
  • I am eating much less than usual. 
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