Comparative study on common diagnostic methods for covert hepatic encephalopathy

Abstract

Objective To evaluate clinical application value of critical flicker frequency (CFF), psychometric hepatic encephalopathy score (PHES) and Stroop test in the diagnosis of covert hepatic encephalopathy (CHE). Methods A total of 110 patients with decompensated liver cirrhosis and 54 individuals without liver diseases were enrolled as control group. According to PHES<-4 points as reference threshold for CHE, the threshold of CFF and time of Stroop test for CHE diagnosis was caculated. Positive results of at least two of PHES, CFF and Stroop tests was considered as the gold standard for CHE diagnosis, and then the value of these three methods in CHE diagnosis was evaluated. Student′s t test and receiver operating characteristic curve (ROC) were used for statistical analysis. Results Among the 110 patients with liver cirrhosis, 40 patients had no hepatic encephalopathy (HE0), 52 patients had CHE, and 18 patients had grade 2 hepatic encephalopathy (HE2). The CFF value and total time of Stroop test of control group were (43.70±1.92) Hz and (201.17±20.65) s, respectively. The CFF value of HE0 group was (41.40±1.85) Hz, which was higher than that of CHE group ((38.33±2.32) Hz), and the difference was statistically significant (t=-7.116, P<0.01). The total time of Stroop test of HE0 group was (197.91±26.68) s, which was shorter than that of CHE group ((253.24±33.33) s), and the difference was statistically significant (t=8.936, P<0.01). When PHES<-4 points was considered as a reference threshold of CHE, the threshold of CFF for CHE diagnosis was 39 Hz, the sensitivity was 94.9% and the specificity was 73.1%, the area under the curve (AUC) was 0.879. The threshold of the total time of Stroop test for CHE diagnosis was 233.80 s, the sensitivity was 83.3% and the specificity was 71.1%, the AUC was 0.803.The completion time of the number connection test (NCT)-A, NCT-B and digit symbol test (DST), which were there of five subtests of PHES, of CHE group were (80.27±36.05) s, (124.18±55.96) s and (25.03±8.23) s, respectively, compared with those of HE0 patients ((56.68±18.82) s, (80.00±25.58) s and (34.68±8.75) s, respectively), the differences were statistically significant (t=3.691, 4.108 and -4.780; all P<0.01). Compared with the results of combined PHES and Stroop test in the diagnosis of HE0, CHE and HE2, the consistency rates of CFF<39 Hz as threshold for diagnosis were 95.0%, 61.5% and 100.0%, respectively. Conclusions NCT-A, NCT-B and DST three subtests of PHES have higher efficiency in CHE diagnosis. CFF and Stroop test are also reliable screening methods for CHE, with advantage of objectivity and high specificity. Key words: Liver cirrhosis; Hepatic encephalopathy; Critical flicker frequency; Psychometric hepatic encephalopathy score; Stroop test