Minimal hepatic encephalopathy is associated with motor vehicle crashes: the reality beyond the driving test

Abstract

Patients with minimal hepatic encephalopathy (MHE) have impaired driving skills, but association of MHE with motor vehicle crashes is unclear. Standard psychometric tests (SPT) or inhibitory control test (ICT) can be used to diagnose MHE. The aim was to determine the association of MHE with crashes and traffic violations over the preceding year and on 1-year follow-up. Patients with cirrhosis were diagnosed with MHE by ICT (MHEICT) and SPT (MHESPT). Self and department-of-transportation (DOT)-reports were used to determine crashes and violations over the preceding year. Agreement between self and DOT-reports was analyzed. Patients then underwent 1-year follow-up for crash/violation occurrence. Crashes in those with/without MHEICT and MHESPT were compared. 167 patients with cirrhosis had DOT-reports, of which 120 also had self-reports. A significantly higher proportion of MHEICT patients with cirrhosis experienced crashes in the preceding year compared to those without MHE by self-report (17% vs 0.0%, P = 0.0004) and DOT-reports (17% vs 3%, P = 0.004, relative risk: 5.77). SPT did not differentiate between those with/without crashes. A significantly higher proportion of patients with crashes had MHEICT compared to MHESPT, both self-reported (100% vs 50%, P = 0.03) and DOT-reported (89% vs 44%, P = 0.01). There was excellent agreement between self and DOT-reports for crashes and violations (Kappa 0.90 and 0.80). 109 patients were followed prospectively. MHEICT patients had a significantly higher future crashes/violations compared to those without (22% vs 7%, P = 0.03) but MHESPT did not. MHEICT (Odds ratio: 4.51) and prior year crash/violation (Odds ratio: 2.96) were significantly associated with future crash/violation occurrence.

Conclusion: Patients with cirrhosis and MHEICT have a significantly higher crash rate over the preceding year and on prospective follow-up compared to patients without MHE. ICT, but not SPT performance is significantly associated with prior and future crashes and violations. There was an excellent agreement between self- and DOT-reports.

Figure 1. Patient flow through the study

Patient flow throughout the study is displayed. At each stage, the number diagnosed with MHE using ICT and SPT are displayed. 47 patients only had DOT reports while 120 had both self and DOT assessments. Those 120 were used to study agreement between the self and DOT assessments. MHE: minimal hepatic encephalopathy, ICT: inhibitory control test, SPT: standard psychometric tests, DOT: department of transportation, MHE ICT+: those diagnosed with MHE using ICT, MHE SPT+: those diagnosed with MHE using SPT.

Figure 2

Figure 2a: Comparison of the mode of diagnosis of MHE with the motor vehicle crashes reported by the department of transportation in patients with cirrhosis. Detailed patient flow according to DOT-report of the patients with motor vehicle crashes who were diagnosed with MHE using ICT or SPT. A total of 167 patients were given both SPT and ICT and their subsequent classification according to DOT-reported motor vehicle crashes within the past 1 year and their comparison is shown. Figure 2b: Comparison of the mode of diagnosis of MHE with motor vehicle crashes self-reported by the patients with cirrhosis. Detailed patient flow according to self-report of the patients with motor vehicle crashes who were diagnosed with MHE using ICT or SPT. A total of 120 patients were given both SPT and ICT and their subsequent classification according to self-reported motor vehicle crashes within the past 1 year and their comparison is shown. MHE: minimal hepatic encephalopathy, ICT: inhibitory control test, SPT: standard psychometric tests, MHE ICT: patients diagnosed with MHE using ICT, MHE SPT: patients diagnosed with MHE using SPT.

Figure 2

Figure 2a: Comparison of the mode of diagnosis of MHE with the motor vehicle crashes reported by the department of transportation in patients with cirrhosis. Detailed patient flow according to DOT-report of the patients with motor vehicle crashes who were diagnosed with MHE using ICT or SPT. A total of 167 patients were given both SPT and ICT and their subsequent classification according to DOT-reported motor vehicle crashes within the past 1 year and their comparison is shown. Figure 2b: Comparison of the mode of diagnosis of MHE with motor vehicle crashes self-reported by the patients with cirrhosis. Detailed patient flow according to self-report of the patients with motor vehicle crashes who were diagnosed with MHE using ICT or SPT. A total of 120 patients were given both SPT and ICT and their subsequent classification according to self-reported motor vehicle crashes within the past 1 year and their comparison is shown. MHE: minimal hepatic encephalopathy, ICT: inhibitory control test, SPT: standard psychometric tests, MHE ICT: patients diagnosed with MHE using ICT, MHE SPT: patients diagnosed with MHE using SPT.

Figure 3. Motor vehicle crash occurrence and mode of diagnosis of MHE

Percentage of patients with motor vehicle crashes with MHE according to ICT or SPT are displayed in this figure. 100% of patients with self-reported crashes had MHE according to ICT compared to 50% who had MHE according to SPT which was highly significant. Similarly, 89% of patients with DOT-reported crashes had MHE according to ICT compared to only 44% of those diagnosed by MHE using SPT. MHE: minimal hepatic encephalopathy, ICT: inhibitory control test, SPT: standard psychometric tests, DOT: department of transportation.

Figure 4

Figure 4a: Percent of patients with crashes by self report. Percentage of patients who had motor vehicle crashes according to self-report in those diagnosed with MHE using ICT (17%) were significantly higher compared to 0% in those who were negative for MHE using ICT. In contrast, there was no significant difference in the percentage of patients with MHE according to SPT performance. The relative risk for crashes according to MHE ICT status was 5.77. Figure 4b: Percent of patients with crashes by DOT reports. Similarly there was a significantly higher percentage of patients diagnosed with MHE using ICT who had DOT-reported motor vehicle crashes (16%) compared to those who were negative by ICT (3%). Again, there was no significant difference in those with and without MHE diagnosed by SPT vis-à-vis motor vehicle crashes reported by the DOT.