Relationship between clock and star drawing and the degree of hepatic encephalopathy

Purpose of the study Current hepatic encephalopathy grading tools are limited because of complexity or subjectivity. The degree of constructional apraxia could serve as a simple, objective and reproducible tool to grade encephalopathy. Study design In this cross-sectional study of patients with chronic liver disease, the degree of constructional apraxia was judged by their ability to copy a star and clock face and compared with conventional encephalopathy grading by the West Haven Criteria (WHC) and the Porto Systemic Encephalopathy Index (PSEI). Three blinded observers independently graded the figures. Sensitivity, specificity and positive predictive value (PPV) of clock and star scores (score 0 implying no encephalopathy and >0 hepatic encephalopathy) were assessed against conventional scoring systems (WHC grade >0 or PSEI ≥0.33 indicating encephalopathy). Mosaic and box plots were generated to assess if the degree of constructional apraxia correlated with the severity of encephalopathy. Results 71 patients were studied between October 2008 and July 2009; 11 (15.4%) had WHC grade 0, 32 (45%) grade 1, and 28 (39.4%) grades 2 and 3 encephalopathy. The sensitivity, specificity and PPV of the clock drawing for the diagnosis of encephalopathy was 85%, 80%, and 96%, respectively, and 77%, 70%, and 94%, respectively, for the star drawing. Box plots and intervals on mean PSEI showed an increasing relationship between clock/star scores and PSEI. There was substantial agreement between WHC and clock (weighted k 0.61) and star scores (weighted k 0.71). Inter-observer reliability was at least 0.70 for star and at least 0.79 for the clock score. Conclusion Clock and star drawing may serve as reproducible, inexpensive bedside tools for diagnosing and grading the severity of hepatic encephalopathy.