Diagnosis and Treatment of Minimal Hepatic Encephalopathy to Prevent Motor Vehicle Accidents: A Cost-Effectiveness Analysis

Abstract

Minimal hepatic encephalopathy (MHE) in cirrhosis is associated with impaired driving skills and increased risk of motor vehicle accidents (MVAs). Detection and treatment of MHE has the potential to reduce costs and morbidity associated with MVAs.

Methods

We conducted a cost-effectiveness analysis to assess the benefits of different strategies of MHE diagnosis and treatment for reducing MVA-related societal costs. The analyses compared five MHE management strategies: (1) presumptive treatment of all cirrhotics; (2) diagnosis by neuropsychological exam (NPE) with treatment; (3) diagnosis by standard psychometric tests (SPT) with treatment; (4) diagnosis by rapid screening using inhibitory control test (ICT) with treatment; and (5) no MHE diagnosis or treatment (status quo). Treatments considered were lactulose or rifaximin, which were assumed to reduce the MVA rate to the level of similarly-aged non-cirrhotics with benefit adjusted for treatment compliance. A Markov model followed a simulated cohort of 1000 cirrhotics without overt HE(OHE), from entry into treatment, through MHE development, and later, OHE, when they exited the modeled cohort. Follow-up was for 5 years and included biannual MHE testing. The societal cost of a single MVA was estimated at $42,100.

Results

All 4 strategies with lactulose were cost-saving compared to the status quo. Diagnosis with ICT and lactulose was the most cost-effective approach (cost/MVA prevented: $24,454 ICT; $25,470 SPT; $30,469 presumptive treatment and $33,742 NPE). Net program savings over 5 years ranged from $1.7 to 3.6 million depending on the strategy. Rifaximin therapy was not cost-saving at current prices but would become so at a monthly cost <$353.

Conclusion

Detection of MHE, especially using the ICT, and subsequent treatment with lactulose could substantially reduce societal costs by preventing MVAs.

Minimal hepatic encephalopathy (MHE) is present in approximately 55% of cirrhotic patients tested (1-4). MHE increases the risk of development of overt hepatic encephalopathy (OHE) and adversely affects survival (5). MHE also is associated with impaired driving skills and a significantly higher risk of motor vehicle crashes (6, 7) due to the attention and visuo-motor coordination deficits associated with this condition. Driving impairment is highly correlated with diminished psychometric performance (8-10). There are several methods for the diagnosis of MHE, including a comprehensive neuropsychological exam, standard psychometric batteries, neuro-physiological testing and computerized testing (11-13). These modalities are usually copyrighted and require psychological or neurological expertise for procuring, administration and interpretation in the US, increasing associated costs and reducing access(1). An AASLD survey demonstrated that the majority of hepatologists were not able to test cirrhotic patients for MHE partly due to the lack of availability of testing techniques (14). High-sensitivity tests that can be administered by personnel without specialized expertise, such as the inhibitory control test (ICT)—offer a potentially cost-effective method for diagnosing MHE (6, 15, 16). The ICT is a computerized test of attention and response inhibition which is inexpensive and is well correlated with driving impairment (6, 9, 15). Abnormalities in ICT and standard psychometric tests have been shown to be related to driving offenses and vehicular crashes (6, 17, 18).

The societal costs associated with motor vehicle accidents include productivity losses, medical expenses, motor vehicle damage, employers’ uninsured costs, and administrative expenses (19). The high cost of vehicular accidents—estimated at more than $200 billion per year in the U.S.(20)—necessitates investigation of treatable forms of driving impairment, such as MHE. Lactulose therapy has been tested extensively for patients diagnosed with MHE (13). Lactulose is inexpensive and has been shown to reverse MHE-based performance deficits on psychometric tests (10, 21, 22). However, lactulose adherence is relatively poor, in large part due to gastrointestinal adverse effects (10, 21-23). Rifaximin, which also has been used as a therapy for MHE(24-26), has a much better adherence profile. Moreover, rifaximin has been shown to improve driving simulator performance in a placebo-controlled randomized trial(25).

We report here the results of a model-based cost-effectiveness of MHE diagnosis and subsequent pharmaceutical treatment (lactulose or rifaximin) to reduce motor vehicle accidents among cirrhotic patients. The analyses compared 4 potential strategies for diagnosing and treating MHEwith a no-treatment alternative. Because the effectiveness of pharmaceutical treatments with respect to reducing accidents among treated patients has not been well established, we conducted extensive sensitivity analyses around this key parameter. The aim was to provide a cost-effectiveness platform for MHE diagnosis and treatment from a societal perspective and tailored to individual treatment options available in the United States.

Methods

The cost-effectiveness analysis combined a Markov model of progression from cirrhosis without minimal hepatic encephalopathy, to MHE, to overt hepatic encephalopathy (OHE), with empirically-derived and literature-based estimates of MHE diagnostic tests and treatment parameters and motor vehicle accident-related parameters. The analysis adopted a societal perspective and included time costs borne by patients, as well as the societal costs associated with MVAs. All future costs and benefits were discounted at a 3% annual rate (0% and 5% in the sensitivity analyses) in accordance with recommended practice (27). Results were expressed in base-year 2010 dollars.

The Markov model followed a simulated cohort of 1000 cirrhotic patients with compensated liver disease and without OHE, from entry into treatment (at which point they might or might not have MHE), through the potential development of MHE, and later, OHE, at which time they exited the modeled cohort. The model assumed that cirrhotic patients were screening for MHE on a semi-annual basis (12, 13). State changes within the Markov model also occurred at 6-month intervals. Annual state-transition probabilities, from non-MHE cirrhosis to MHE, and from MHE to OHE, were derived from a published study (28). Six-month state-transition values were derived from these annual probabilities using the equation: p(6 mo) = 1 − (1 − p(12 mo))^0.5. The baseline prevalence of MHE was set to 55% (2-5, 15, 21, 24, 29). The simulated cohort of cirrhotic patients was followed for a total of 5 years.

The main analysis compared 4 diagnostic strategies: 1) presumptive treatment of all cirrhotic patients (100% sensitivity); 2) rapid screening using the inhibitory control test (sensitivity = 90% and specificity = 85% based on previous studies; (6, 15); 3) standard psychometric test battery (sensitivity = 95% and specificity = 85%); and 4) full neuropsychological examination (the “gold standard”: 100% sensitive and specific). Test costs and patient time for the 4 diagnostic test options were based on the authors’ experiences at their home institutions (15) (see Table 1). The cost for SPT was varied to reflect its use in other countries. Patient time was valued at $19.25 per hour based on Bureau of Labor Statistics averages for persons aged 45 to 64, assuming a 90% employment rate (30).

Table 1.

Diagnostic Test Parameters

	Test cost	Time (hours)	Base-case sensitivity	Base-case specificity
Presumptive treatment	$0	0.0	100%	0%
Inhibitory control test (ICT)	$20	0.25	90%	85%
Standard psychometric test (SPT)	$105	0.50	95%	85%
Neuropsychological examination	$769	6.0	100%	100%

The analyses assumed that patients who tested MHE-positive would be treated with either lactulose at a monthly cost of $150 (31) or rifaximin 550mg BID at a monthly cost of $1120 to reduce cognitive impairment and, consequently, the likelihood of involvement in a motor vehicle crash(24-26). Limited information is available from randomized clinical trials regarding lactulose adherence (10, 21-23). Adherence is greater than 80% in MHE clinical trials, but gastrointestinal adverse effects often force poor compliance or reduction in dosage in patients outside of trials (32-34). In the main analysis lactulose adherence was set to 70% (range = 50% to 90%) and rifaximin adherence was set to 95% (range = 90% to 99%).

Recent studies have found a 0.17 to 0.19 per-person annual crash rate for patients with MHE, versus no MVAs among cirrhotic patients without MHE (6, 17, 18). The analyses assumed that effective pharmaceutical therapy would reduce the crash rate to the baseline level, 0.039, for a similarly-aged cohort of persons without cirrhosis (20), and that patients who developed OHE discontinued driving but those who developed decompensated cirrhosis due to reasons other than OHE were still able to drive.

The cost-effectiveness analysis compared the overall cost of MHE diagnosis and treatment (including patient time costs) to the societal savings that are realized by preventing MVAs through effective management of the cognitive impairment observed in MHE patients. The cost-effectiveness ratio for a particular diagnostic strategy (cost per MVA prevented) can be expressed as (C + Tk) / EAR, where C is the total cost of screening patients for MHE during the 5-year period; T is the total number of treatment months for patients who test (true or false) positive for MHE; k is the cost of treatment, per month; E is the number of effective treatment months (i.e., the number of treatment-adherent months for true positives); A is the number of accidents per month for patients with untreated MHE; and R is the reduction in the accident rate due to effective treatment. The cost-effectiveness ratio can be interpreted as the total (gross) cost per MVA prevented by the screening strategy when MHE-positive diagnoses are followed by a specific treatment protocol.

National Highway and Traffic Administration data estimate the average societal cost per MVA to be $42,100 (20). Consequently, the net cost of a testing/treatment strategy equals (C + Tk) − ($42,100)EAR. If this value is negative, then the diagnostic/treatment strategy is cost-saving (i.e., the monetary benefits of the testing and treatment program exceed the costs). When more than one diagnostic strategy is cost-saving, the preferred strategy is the one with the smaller net cost because it generates greater societal savings. If no strategy is cost-saving, the preferred strategy is the one with the smallest cost-effectiveness ratio. Naturally, if one strategy is cost-saving and another is not, the one that generates societal savings is preferred over the one with a positive net cost.

Table 2 lists key modeling parameters, values used in the analyses, and the sources of these parameter values. One-way (univariate) analyses were conducted for all key parameters to account for uncertainty in base-case estimates. Additional sensitivity analyses were conducted as needed.

Table 2.

Model Parameter Values

Parameter	Valuesa	Source
Prevalence of MHE among patients	55% (50% – 60%)	Das et al.(2), Sharma et al.(3), Gitlin et al.(4), Romero-Gomez et al.(5), Rikkers et al.(29)
Annual progression: No MHE to MHE	19% (0% – 50%)	Huang et al.(28)
Annual progression: MHE to OHE	23% (0% – 50%)	Huang et al.(28)
Rapid test (ICT) sensitivity	90% (70% – 95%)	Bajaj et al., Amodio et al.(6, 15, 16)
Rapid test (ICT) specificity	85% (80% – 90%)	Bajaj et al., Amodio et al.(6, 15, 16)
Standard psychological test (SPT) sensitivity	95% (90% – 100%)	Weissenborn et al.(35).
Standard psychological test (SPT) specificity	85% (80% – 90%)	Weissenborn et al.(35).
Lactulose adherence	70% (50% – 90%)	Dhiman et al.(10), Prasad et al.(16), Horsmans et al.(18)
Rifaximin adherence	95% (90% – 99%)	Bajaj et al.(25), Sidhu et al.(24),
Accidents per year, untreated MHE	0.18 (0.17 – 0.19)	Bajaj et al. and Gad et al. (6, 17, 18)
Accidents per year, treated/adherent MHE	0.039 (0.033 – 0.045)	NHTSA (26) (age = 45-65) Bajaj et al (17)
Value of patient time, per hour	$19.25 (0 – $21.50)	Bureau of Labor Statistics(30) (age = 45-65)
Economic discount rate	3% (0% – 5%)	Gold et al.(27)

^aBase-case value (values examined in sensitivity analyses) MHE: minimal hepatic encephalopathy, OHE: overt hepatic encephalopathy, ICT: inhibitory control test.

Results

The results of the main analysis for lactulose therapy are presented in Table 3. Diagnosis of MHE followed by lactulose therapy was cost-saving for all 4 of the diagnostic strategies considered in the analyses compared to the status quo of no testing or treatment. Rapid screening using ICT was the most cost-effective of the diagnostic strategies, just marginally ahead of the SPT. The cost per accident prevented in this scenario ($24,454 over the 5-year analysis period) was considerably less than the societal cost associated with a single MVA ($42,100). Screening 1000 patients at 6-month intervals and treating MHE-positive patients with lactulose would cost $4.9 million and prevent 202 crashes over 5 years. During this time the rapid ICT screening plus lactulose treatment scenario would generate $8.5 million in crash-related savings, for a net savings of $3.6 million. Similar results were obtained for the standard tests, which was just slightly less cost effective than the ICT (see Table 3). ICT remained cost-effective even when the SPT was reduced to $35; if the cost of SPT reduced below $35, then it became the most cost-effective strategy. The remaining diagnostic strategies (presumptive treatment and comprehensive neuropsychological exam) each prevented more crashes than rapid ICT screening or standard tests, but did so at substantially greater costs.

Table 3.

Cost-Effectiveness of MHE Screening and Treatment with Lactulose: Main Results over 5 Years

	Presumptive treatment	Inhibitory control test	Standard psychometric battery	Neuro-psychological exam
Total program cost ($)	6.3M	4.9M	5.2M	6.9M
Screening/testing costs ($)	0	49,769	257,679	2.8M
Patient time costs ($)	0	11,976	23,621	416,952
Treatment costs ($)	6.3M	4.9M	4.9M	3.8M
Accidents prevented	205.94	202.20	204.164	205.94
Societal savings ($)	8.7M	8.5M	8.6M	8.7M
Net program cost ($)	-2.4M	-3.6M	-3.4M	-1.7M
Cost per accident prevented ($)	30,469	24,454	25,470	33,742

MHE diagnosis followed by lactulose therapy remained cost-saving for all 4 diagnostic strategies and for all of the parameter values examined in the univariate sensitivity analyses (Table 4), with two exceptions. The results were somewhat sensitive to the lactulose adherence rate, which was varied from 50% to 90%, and to the MHE and OHE progression rates. However, this uncertainty did not change the cost-effectiveness rankings of the 4 diagnostic screening options.

Table 4.

5-Year Sensitivity Analysis Results: Cost per Accident Prevented ($)^*

Parameter (base-case value)	PT	ICT	SPT	NPE
MHE prevalence (55%)
50%	32,405	25,421	26,546	35,697
60%	28,685	23,562	24,478	31,939
Annual progression: No MHE to MHE (19%)
0%	42,929	32,221	33,768	45,647
50%	23,485	20,332	21,022	26,821
Annual progression: MHE to OHE (23%)
0%	25,930	22,122	22,773	27,988
50%	38,874	28,852	30,506	44,396
ICT sensitivity (90%)
70%	N/A	24,804	N/A	N/A
95%	N/A	24,390	N/A	N/A
ICT specificity (85%)
80%	N/A	25,596	N/A	N/A
90%	N/A	22,997	N/A	N/A
SPT sensitivity (95%)
90%	N/A	N/A	25,559	N/A
100%	N/A	N/A	25,390	N/A
SPT specificity (85%)
80%	N/A	N/A	26,494	N/A
90%	N/A	N/A	24,162	N/A
Lactulose adherence (70%)
50%	42,657	34,236	35,658	47,238
90%	23,698	19,020	19,810	26,243
Accidents per year, untreated MHE (0.180)
0.170	32,795	26,321	27,414	36,317
0.190	28,451	22,835	23,783	31,507
Accidents per year, treated MHE (0.039)
0.033	29,225	23,456	24,430	32,364
0.045	31,823	25,541	26,602	35,241
Value of patient time, per hour ($19.25)
$0	30,469	24,395	25,354	31,717
$21.50	30,469	24,461	25,483	33,978
Economic discount rate (3%)
0%	30,403	24,511	25,499	33,561
5%	30,512	24,417	25,451	33,860

PT: presumptive treatment; ICT: inhibitory control test; SPT: standard test battery; NPE: neuropsychological examination; MHE: minimal hepatic encephalopathy; OHE: overt hepatic encephalopathy.

^*Base-case results (cost per accident prevented): $30,469 for presumptive treatment; $24,454 for ICT; $25,470 for SPT; and $33,742 for neuropsychological exam.

The main analysis assumed that effective and adherent MHE treatment would reduce the crash rate from 0.18 to the baseline level, 0.039, for a similarly-aged cohort of persons without cirrhosis—that is, that it would reduce the accident rate by 78.3%. Although rifaximin has been shown to improve simulator performance, the effectiveness of lactulose or rifaximin treatment with respect to reducing crashes among treated patients has not been well established. Therefore, we conducted an additional sensitivity analysis around this key parameter. As illustrated in Fig. 1, ICT screening plus lactulose treatment would remain cost-saving even if the reduction in crash rates were as small as 46%, rather than 78.3% as assumed in the base-case analysis.

Fig. 1.

Cost per accident prevented for the 4 diagnostic strategies considered in the analyses when combined with lactulose treatment. The inhibitory control test (ICT) plus lactulose treatment is cost-saving for 44% and greater reductions in the accident rate for MHE patients. Larger accident rate reductions are necessary to achieve cost savings in the standard psychometric test battery (SPT), the neuropsychological exam, and the presumptive treatment plus lactulose scenarios.

The results of the analyses for rifaximin therapy differed substantively from those for lactulose in two main respects. First, the neuropsychological exam rather than ICT was the most cost-effective of the 4 screening strategies, and second, none of the 4 screening strategies was cost-saving when paired with rifaximin treatment due to the high monthly cost of this treatment. The cost per crash prevented ranged from $111,760 for the neuropsychological exam to more than $167,000 for presumptive treatment.

We conducted a threshold analysis to determine by how much the monthly cost of rifaximin would need to be reduced in order for screening plus rifaximin treatment to be cost-saving. This analysis indicated that ICT plus rifaximin would be cost saving is rifaximin cost no more than $353 per month. Of note, at this cost, ICT was the most cost-effective of the 4 diagnostic strategies, as shown in Fig. 2.

Fig. 2.

Cost per accident prevented for the 4 diagnostic strategies considered in the analyses when combined with Rifaximin treatment. The inhibitory control test (ICT) plus Rifaximin treatment would be cost-saving if the monthly cost of Rifaximin were less than $353 (cf, $348 for the standard psychological test battery (SPT); $342 for a neuropsychological exam; and $281 for presumptive treatment).

Discussion

There are no current guidelines for the diagnosis or treatment of MHE in patients with cirrhosis, despite ample evidence that patients with MHE have a higher rate of motor vehicle crashes, poor quality of life, and increased progression to OHE (5). The results of the preceding analyses indicate that diagnosis of MHE followed by lactulose therapy could result in substantial societal cost savings by preventing MVAs among MHE patients. In contrast, because of its high monthly cost, treatment with rifaximin is unlikely to generate overall cost savings unless the rifaximin monthly cost is substantially reduced(28). The results also suggest that, when combined with lactulose treatment, screening using the ICT or a standard test battery is more cost-effective than either presumptive treatment of all cirrhotic patients or conducting comprehensive neuropsychological examinations to detect MHE.

We used the neuropsychological examination as the gold standard because it involves an evaluation of multiple dimensions including psychologist interview, detailed cognitive testing, mood, psychiatric and substance abuse disorder assessments. This is usually performed as part of pre-transplant evaluation and gives a deeper appreciation of factors that could confound the ultimate cognitive testing results. Before performing the ICT or SPT, this information is sought from the medical record or patient interview to exclude confounders. Therefore this was used as the standard to which the smaller cognitive batteries are compared. The standard batteries vary between investigators and studies but are a collection of several recommended cognitive tests such as number connection test-A/B, digit symbol, block design tests which are also components of the Psychometric Hepatic Encephalopathy Score (PHES)(1, 35). While these tests are recommended and validated for diagnosis of MHE, most components do not have norms for the US population (36). In addition, in the US, a psychologist is required to procure, administer and interpret the results, adding to the barriers in testing. Therefore, unlike other countries, the use of standard tests for the diagnosis of MHE clinically remains difficult in the US. Tests such as the ICT have been used that, unlike standard psychologist-administered test batteries—is not copyrighted (6). The ICT costs less than a standard psychological test battery since it can be administered by clinical assistants with minimal training (15). Similar results were obtained for the ICT and SPT in this study, indicating that both these are cost-saving and could potentially be used depending on the availability of expertise and norms. ICT remained cost-effective compared to SPT even when the cost of SPT reduced to less than $35; this would be applicable in other countries provided all other parameters e.g. cost for rifaximin and lactulose.

Another possible strategy, especially in populations that have a high prevalence of MHE, would be to presumptively treat every cirrhotic patient with lactulose or rifaximin without the prior diagnostic testing. Although this strategy is theoretically appealing, the adverse effects of lactulose are associated with poor adherence even in OHE patients who have significant symptoms from their encephalopathy (34, 37). It is unlikely that patients with MHE—most of whom do not suffer from any specific symptoms and have poor insight—would be adherent on a medication with these adverse effects (38). Adherence would potentially be higher on rifaximin; however this strategy is limited by the associated costs which are the highest for the presumptive treatment with rifaximin category. Adherence would also be expected to increase if patients’ impaired psychometric performance were demonstrated to them(39). Therefore, the additional step of testing (e.g., using the ICT or a standard psychometric battery) and selectively treating only those impaired would not only increase adherence but also avoid the unnecessary adverse effects or costs of therapy in those who do not have cognitive abnormalities.

There is ample evidence regarding the use of rifaximin in the therapy of both MHE and overt HE(24, 25, 40). It is well-tolerated and had good efficacy in these conditions. However, the cost of rifaximin therapy is almost ten times that of lactulose(26). Therefore we found in our analysis that in contrast to the findings for lactulose, the comprehensive neuropsychological exam was the most cost-effective diagnostic strategy when combined with rifaximin therapy (though it was not cost-saving). This finding is due to the high cost of rifaximin, which in turn places a premium on reducing the number of patients who test false positive and are unnecessarily started on rifaximin. The analyses assumed 100% specificity for neuropsychological exams, which reduced the number of false positives to zero. The supplementary threshold analysis indicated that ICT followed by rifaximin treatment would be cost-saving if the monthly cost of rifaximin were reduced to no more than $353 per month. Of note, at this cost, ICT rather than the neuropsychological exam was the most cost-effective of the 4 diagnostic strategies.

Despite uncertainties in several key parameter values, the results of the analysis were quite robust. When combined with lactulose therapy, all 4 diagnostic strategies were cost-saving for all but a small number of the parameter values examined in the univariate sensitivity analyses. However, if all model parameters were set to their least favorable values, screening plus lactulose might no longer be cost-saving. Given the generous margins of the sensitivity analyses, this is not likely to be a concern. The limitations of the assumptions, specifically regarding reduction in MVA with lactulose or rifaximin, are evident. However a trial that actually randomizes MHE patients into placebo or drug, given the prior background evidence, and follows them up for several years for possible MVA development is likely to be very expensive and impossible to conduct ethically. Therefore extensive sensitivity parameters around assumptions around which there are no specific data available were made.

The cost-effectiveness analyses focused on motor vehicle crashes as an objective endpoint that is known to be associated with the attention deficits and psychometric impairments present in MHE (6). Other clinically relevant endpoints of MHE therapy could include development of overt HE, improvement of health-related quality of life (HRQOL) and employment. The analyses did not consider potential improvements in the HRQOL of patients diagnosed with MHE and subsequently treated since an objective endpoint such as MVA was preferred (21, 24, 25). And, the results of the analyses presented above indicate that diagnosis and treatment of MHE can be cost-saving when the potential reduction in MVAs is considered.

These assumptions are solely based for the practice, logistic and research constraints that exist in the US and cannot be readily applied to countries in which standard batteries are freely available or where medications other than lactulose and rifaximin are in widespread use. We also did not include neuro-physiological modalities such as EEG or evoked potentials since they require neurological expertise with added costs. Critical flicker frequency was also not considered, even though it has good validity in MHE, because of its lack of availability of norms and equipment required to use it. However, it is well known that MHE affects several aspects of cognition and all testing strategies can detect some variant of the spectrum of the neuro-cognitive impairment in cirrhosis. We only included the ones that are being used in clinical research in the US at this time.

The analyses provide strong evidence that the development and implementation of effective strategies to diagnose and treat MHE could save society money by reducing the incidence of motor vehicle crashes among MHE patients. Further investigation into the societal cost of cognitive dysfunction in cirrhosis is important to encourage routine diagnosis and therapy of MHE beyond the research setting.

Table 5.

Cost-Effectiveness of MHE Screening and Treatment with Rifaximin: Main Results over 5 Years

	Presumptive treatment	Inhibitory control test	Standard psychometric battery	Neuro-psychological exam
Total program cost ($)	46.9M	36.5M	37.0M	31.2M
Screening/testing costs ($)	0	49,769	257,679	2.8M
Patient time costs ($)	0	11,976	23,621	416,952
Treatment costs ($)	46.9M	36.5M	36.7M	28.0M
Accidents prevented	279.49	274.41	277.07	279.49
Societal savings ($)	11.8M	11.6M	11.7M	11.8M
Net program cost ($)	35.1M	25.0M	25.3M	19.5M
Cost per accident prevented ($)	167,633	133,085	133,564	111,760

List of Abbreviations

MHE

minimal hepatic encephalopathy

OHE

overt hepatic encephalopathy

MVA

motor vehicle accident

ICT

inhibitory control test

SPT

standard psychometric test battery

QOL

quality of life