Clinical and MRI Predictors of Conversion From Mild Behavioural Impairment to Dementia

Correlates of Mild Behavioral Impairment in Older Adults: Protocol for a Scoping Review

BACKGROUND

Understanding mild behavioral impairment, a relatively recent notion in neuropsychological studies, provides significant insights into early behavioral indicators of cognitive decline and predicts the onset of dementia in older adults. Although the importance of understanding mild behavioral impairment is acknowledged, comprehensive reviews of its correlates with older adults are limited.

OBJECTIVE

This scoping review aims to identify the impact of mild behavioral impairment on health outcomes in older adults and the factors associated with mild behavioral impairment.

METHODS

The review will adhere to the Joanna Briggs Institute's methodological principles for scoping reviews. We will include studies focusing mainly on mild behavioral impairment in older adults, with the literature on this topic being limited to the period from 2003 to the present. Other clinical diagnoses, such as cognitive impairment, Parkinson disease, and multiple sclerosis, will not be included. We will use databases including PubMed (MEDLINE), CINAHL, Web of Science, Embase, PsycINFO, Cochrane, and Scopus for relevant articles published in English. Both gray literature and peer-reviewed articles will be considered during screening. Three independent reviewers will extract data using a predefined data extraction tool. Extracted data will be presented using tables, figures, and a narrative summary aligned with review questions, accompanied by an analysis of study characteristics and categorization of mild behavioral impairment correlates.

RESULTS

The results will be presented as a descriptive summary, structured according to the associated factors related to mild behavioral impairment, and the health outcomes. Additionally, the data on study characteristics will be presented in tabular format. An exploratory search was conducted in July 2023 to establish a comprehensive search strategy, and iterative refinements to the scoping review protocol and formalization of methods were completed. A follow-up search is planned for May 2024, with the aim of submitting the findings for publication in peer-reviewed journals.

CONCLUSIONS

To our knowledge, this would be the first study to map the literature on the health-related factors and outcomes of mild behavioral impairment. The findings will support the development of interventions to prevent the occurrence of mild behavioral impairment and mitigate the negative outcomes of mild behavioral impairment.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/60009.

Contribution of amyloid and putative Lewy body pathologies in neuropsychiatric symptoms

OBJECTIVES

Neuropsychiatric symptom could be useful for detecting patients with prodromal dementia. Similarities and differences in the NPSs between preclinical/prodromal Alzheimer's disease (AD) and prodromal Parkinson's disease dementia (PDD)/Dementia with Lewy bodies (DLB) may exist. This study aimed to compare the NPSs between preclinical/prodromal AD and prodromal PDD/DLB.

METHODS

One hundred and three participants without dementia aged ≥50 years were included in this study. The mild behavioral impairment (MBI) total score and the MBI scores for each domain were calculated using the neuropsychiatric inventory questionnaire score. Participants were divided into five groups based on the clinical diagnosis by neurologists or psychiatrists in each institution based on the results of the amyloid positron emission tomography and dopamine transporter single photon emission computed tomography (DAT-SPECT): Group 1: amyloid-positive and abnormal DAT-SPECT, Group 2: amyloid-negative and abnormal DAT-SPECT, Group 3: amyloid-positive and normal DAT-SPECT, Group 4: mild cognitive impairment unlikely due to AD with normal DAT-SPECT, and Group 5: cognitively normal with amyloid-negative and normal DAT-SPECT.

RESULTS

The MBI abnormal perception or thought content scores were significantly higher in Group 1 than Group 5 (Bonferroni-corrected p = 0.012). The MBI total score (Bonferroni-corrected p = 0.011) and MBI impulse dyscontrol score (Bonferroni-corrected p = 0.033) in Group 4 were significantly higher than those in Group 5.

CONCLUSION

The presence of both amyloid and putative Lewy body pathologies may be associated with psychotic symptoms.

A narrative review on mild behavioural impairment: an exploration into its scientific perspectives

In clinical practice, the admission of patients with late-onset psychological and behavioural symptoms is frequent, regardless of the presence or absence of cognitive decline. These symptoms commonly occur in the prodromal stage of dementia and can precede the onset of dementia. While the concept of Mild Cognitive Impairment (MCI) -which is defined as a level of cognitive impairment insufficient to impact daily functioning- is well established, the notion of Mild Behavioural Impairment (MBI) is not yet widely recognized. However, studies have demonstrated that the presence of MBI in both cognitively normal patients and individuals with MCI is associated with an increased risk of dementia progression. Thus, MBI may serve as a neurobehavioral indicator of pre-dementia risk states. This narrative review aims to discuss the evolution of the term, the relevant clinical aspects, and potential biomarkers that may contribute to the clinical definition of MBI. The objective is to assist clinicians in recognizing the diagnosis and differentiating it from psychiatric syndromes, as well as identifying possible etiologies of neurodegeneration.

Emotional Dysregulation in Mild Behavioral Impairment Is Associated with Reduced Cortical Thickness in the Right Supramarginal Gyrus

BACKGROUND

Mild behavioral impairment (MBI) has attracted attention as a possible precursor symptom of dementia, but its neural basis has not been fully investigated.

OBJECTIVE

We aimed to investigate the relationship between MBI and surface area, cortical thickness, and volume in the temporal and parietal lobes, which are strongly associated with dementia and emotional disorders.

METHODS

This retrospective study evaluated 123 participants: 90 with mild cognitive impairment (MCI), 13 with subjective cognitive decline (SCD), and 20 cognitively healthy (CH). Using analysis of covariance (ANCOVA) with sex, age, and MMSE score as covariates, cortical thickness, surface area, and volume in 10 regions were compared between groups with and without MBI. Groups with MBI emotional dysregulation were also compared with groups without MBI.

RESULTS

ANCOVA revealed significantly smaller cortical thickness in the MBI group's right parahippocampal (p = 0.01) and supramarginal gyri (p = 0.002). After multiple comparison correction, only the right supramarginal gyrus was significantly smaller (p = 0.02). When considering only MBI emotional dysregulation, the right parahippocampal and supramarginal gyrus' cortical thicknesses were significantly smaller in this MBI group (p = 0.03, 0.01). However, multiple comparison correction identified no significant differences (p = 0.14, 0.11).

CONCLUSION

Overall MBI and the emotional dysregulation domains were associated with reduced cortical thickness in the right parahippocampal and supramarginal gyri. Since neurodegeneration in the medial temporal and parietal lobe precedes early Alzheimer's disease (AD), MBI, particularly emotion dysregulation, may predict early AD below the diagnostic threshold.

Neuroimaging of mild behavioral impairment: A systematic review

There are many neuroimaging studies of mild behavioral impairment (MBI), but the results have been somewhat inconsistent. Moreover, it remains unclear whether MBI is a risk factor or prodromal symptom of dementia. Therefore, a systematic review was conducted to summarize the results of neuroimaging studies of MBI and consider whether MBI is a prodromal symptom of dementia in terms of its neural correlates. A systematic review supported by a JSPS Grant-in-Aid for Scientific Research (C) was conducted using MBI neuroimaging studies identified using PubMed, PsycINFO, CINAHL, and Google Scholar on November 1, 2022. The inclusion criteria were (i) neuroimaging study; (ii) research on human subjects; (iii) papers written in English; and (iv) not a case study, review, book, comments, or abstract only. Joanna Briggs Institute critical appraisal checklists were used to assess the quality of selected studies, and 23 structural and functional imaging studies were ultimately included in the systematic review. The structural studies suggested an association of MBI with atrophy in the hippocampus, parahippocampal gyrus, entorhinal cortex, and temporal lobe, whereas the functional studies indicated involvement of an altered default mode network, frontoparietal control network, and salience network in MBI. A limitation in many studies was the use of region-of-interest analysis. The brain areas detected as neural correlates of MBI are considered to be alterations in the early stage of each dementia. Therefore, MBI may emerge against a background of pathological changes in dementia.

A Functional and Neuroanatomical Model of Dehumanization

The dehumanization of others is a major scourge of mankind; however, despite its significance, physicians have little understanding of the neurobiological mechanisms for this behavior. We can learn much about dehumanization from its brain-behavior localization and its manifestations in people with brain disorders. Dehumanization as an act of denying to others human qualities includes two major forms. Animalistic dehumanization (also called infrahumanization) results from increased inhibition of prepotent tendencies for emotional feelings and empathy for others. The mechanism may be increased activity in the inferior frontal gyrus. In contrast, mechanistic dehumanization results from a loss of perception of basic human nature and decreased mind-attribution. The mechanism may be hypofunction of a mentalization network centered in the ventromedial prefrontal cortex and adjacent subgenual anterior cingulate cortex. Whereas developmental factors may promote animalistic dehumanization, brain disorders, such as frontotemporal dementia, primarily promote mechanistic dehumanization. The consideration of these two processes as distinct, with different neurobiological origins, could help guide efforts to mitigate expression of this behavior.

Mild behavioral impairment as a potential marker of predementia risk states in motor neuron diseases

BACKGROUND AND PURPOSE

Mild behavioral impairment (MBI) has been increasingly regarded as the neurobehavioral axis of predementia risk states, but a specific investigation of its detection as a potential marker of prodromal dementia in motor neuron diseases (MNDs) is still lacking. The aims of our study were therefore to explore MBI in MNDs both at onset and over the disease course, and to evaluate its relationship with baseline and longitudinal cognitive features.

METHODS

Sixty MND patients with cognitive/behavioral, mood, and motor examinations were recruited and followed longitudinally for up to 15 months. Associations between baseline MBI symptoms and clinical features were tested using the Spearman correlation coefficient. Based on longitudinal data, relative deltas of variation for each cognitive measure were generated, and linear regression models were then used to evaluate the role of baseline MBI symptoms in predicting longitudinal rates of cognitive decline.

RESULTS

At disease onset, the most impaired MBI domain was affective/emotional dysregulation, followed by impulse dyscontrol, apathy, and social inappropriateness. Greater MBI symptoms correlated with more severe baseline motor, cognitive/behavioral, and mood disturbances (p values from <0.001 to 0.05). Longitudinally, the greatest decline was observed in the affective/emotional dysregulation domain, followed by impulse dyscontrol, apathy, and social inappropriateness. Greater MBI symptoms at onset were significant predictors of more severe longitudinal cognitive decline in both amyotrophic lateral sclerosis (ALS)-specific and ALS-nonspecific functions (p values from <0.001 to 0.03).

CONCLUSIONS

MBI represents a valuable clinical marker of incident cognitive decline in MNDs, and its evaluation has good potential for detecting dementia in its preclinical/prodromal phase.

Behavioral Variant Frontotemporal Dementia and Social and Criminal Transgressions

OBJECTIVE

Behavioral variant frontotemporal dementia (bvFTD) is associated with social and criminal transgressions; studies from countries around the world have documented such behavior in persons with this condition. An overview and analysis of social and criminal transgressions in bvFTD and their potential neurobiological mechanisms can provide a window for understanding the relationship of antisocial behavior and the brain.

METHODS

This review evaluated the literature on the frequency of social and criminal transgressions in bvFTD and the neurobiological disturbances that underlie them.

RESULTS

There is a high frequency of transgressions among patients with bvFTD due to impairments in neurocognition, such as social perception, behavioral regulation, and theory of mind, and impairments in social emotions, such as self-conscious emotions and empathy. Additionally, there is significant evidence for a specific impairment in an innate sense of morality. Alterations in these neurobiological processes result from predominantly right-hemisphere pathology in frontal (ventromedial, orbitofrontal, inferolateral frontal), anterior temporal (amygdala, temporal pole), limbic (anterior cingulate, amygdala), and insular regions.

CONCLUSIONS

Overlapping disturbances in neurocognition, social emotions, and moral reasoning result from disease in the mostly mesial and right-sided frontotemporal network necessary for responding emotionally to others and for behavioral control. With increased sophistication in neurobiological interventions, future goals may be the routine evaluation of these processes among individuals with bvFTD who engage in social and criminal transgressions and the targeting of these neurobiological mechanisms with behavioral, pharmacological, and other interventions.

Establishing an individualized model of conversion from normal cognition to Alzheimer's disease after 4 years, based on cognitive, brain morphology and neuropsychiatric characteristics

OBJECTIVES

The impact of neuropsychiatric symptoms (NPS) on cognitive performance has been reported, and this impact was better defined in the aging population. Yet the potential of using the impact of NPS on brain and cognitive performance in a longitudinal setting, as prediction of conversion - have remained questionable. This study proposes to establish a predictive model of conversion to Alzheimer's disease (AD) and mild cognitive impairment (MCI) based on current cognitive performance, NPS and their associations with brain morphology.

METHODS

156 participants with MCI from the Alzheimer's Disease Neuroimaging Initiative database cognitively stable after a 4-year follow-up were compared to 119 MCI participants who converted to AD. Each participant underwent a neuropsychological assessment evaluating verbal memory, language, executive and visuospatial functions, a neuropsychiatric inventory evaluation and a 3 Tesla MRI. The statistical analyses consisted of 1) baseline comparison between the groups; 2) analysis of covariance model (controlling demographic parameters including functional abilities) to specify the variables that distinguish the two subgroups and; 3) used the significant ANCOVA variables to construct a binary logistic regression model that generates a probability equation to convert to a lower cognitive performance state.

RESULTS

Results showed that MCI who converted to AD in comparison to stable MCI, exhibited a higher NPS prevalence, a lower cognitive performance and a higher number of involved brain structures. Functional abilities, memory performance and the sizes of inferior temporal, hippocampal and amygdala sizes were significant predictors of MCI to AD conversion. We also report two models of conversion that can be implemented on an individual basis for calculating the percentage risk of conversion after 4 years.

CONCLUSION

These analytical methods might be a good way to anticipate cognitive and brain declines.

THE IMPLICATIONS OF FRONTOTEMPORAL DEMENTIA FOR BRAIN DYSFUNCTION IN PSYCHOPATHY

Understanding how psychopathy compares with brain disease can help clarify its underlying mechanisms. This literature review is a broad overview of the neurobiology of psychopathic traits in comparison to behavioral variant frontotemporal dementia (bvFTD), a disorder uniquely associated with criminal behavior. In addition to violation of social norms, both psychopathy and bvFTD result in impaired socioemotional perception and empathy, impulsivity, and altered moral judgment. Despite wide areas of decreased function in psychopathy, structural changes are primarily evident in amygdala and, to a lesser extent, anterior insula, whereas in bvFTD neuropathology involves a wider paralimbic region. In psychopathy, relatively intact medial prefrontal and anterior cingulate cortices facilitate theory of mind and psychopathic traits such as deceitfulness and manipulation, bold fearlessness, and risk-taking behavior. In conclusion, many frontotemporal areas are hypoactive in psychopathy and bvFTD, but differences in dysfunctional connectivity in psychopathy vs. direct involvement in bvFTD potentially explain similarities and differences between these two conditions.

The Role of Hub and Spoke Regions in Theory of Mind in Early Alzheimer's Disease and Frontotemporal Dementia

Theory of mind (ToM, the ability to attribute mental states to others) deficit is a frequent finding in neurodegenerative conditions, mediated by a diffuse brain network confirmed by 18F-FDG-PET and MR imaging, involving frontal, temporal and parietal areas. However, the role of hubs and spokes network regions in ToM performance, and their respective damage, is still unclear. To study this mechanism, we combined ToM testing with brain 18F-FDG-PET imaging in 25 subjects with mild cognitive impairment due to Alzheimer’s disease (MCI−AD), 24 subjects with the behavioral variant of frontotemporal dementia (bvFTD) and 40 controls. Regions included in the ToM network were divided into hubs and spokes based on their structural connectivity and distribution of hypometabolism. The hubs of the ToM network were identified in frontal regions in both bvFTD and MCI−AD patients. A mediation analysis revealed that the impact of spokes damage on ToM performance was mediated by the integrity of hubs (p < 0.001), while the impact of hubs damage on ToM performance was independent from the integrity of spokes (p < 0.001). Our findings support the theory that a key role is played by the hubs in ToM deficits, suggesting that hubs could represent a final common pathway leading from the damage of spoke regions to clinical deficits.

Apathy as a Treatment Target in Alzheimer's Disease: Implications for Clinical Trials

Apathy is one of the most prevalent, stable and persistent neuropsychiatric symptom across the neurocognitive disorders spectrum. Recent advances in understanding of phenomenology, neurobiology and intervention trials highlight apathy as an important target for clinical intervention. We conducted a comprehensive review and critical evaluation of recent advances to determine the evidence-based suggestions for future trial designs. This review focused on 4 key areas: 1) pre-dementia states; 2) assessment; 3) mechanisms/biomarkers and 4) treatment/intervention efficacy. Considerable progress has been made in understanding apathy as a treatment target and appreciating pharmacological and non-pharmacological apathy treatment interventions. Areas requiring greater investigation include: diagnostic procedures, symptom measurement, understanding the biological mechanisms/biomarkers of apathy, and a well-formed approach to the development of treatment strategies. A better understanding of the subdomains and biological mechanisms of apathy will advance apathy as a treatment target for clinical trials.

Mild behavioral impairment: measurement and clinical correlates of a novel marker of preclinical Alzheimer's disease

BACKGROUND

Late-life onset neuropsychiatric symptoms are established risk factors for dementia. The mild behavioral impairment (MBI) diagnostic framework was designed to standardize assessment to determine dementia risk better. In this Mini Review, we summarize the emerging clinical and biomarker evidence, which suggests that for some, MBI is a marker of preclinical Alzheimer's disease. MAIN: MBI is generally more common in those with greater cognitive impairment. In community and clinical samples, frequency is around 10-15%. Mounting evidence in cognitively normal samples links MBI symptoms with known AD biomarkers for amyloid, tau, and neurodegeneration, as well as AD risk genes. Clinical studies have found detectable differences in cognition associated with MBI in cognitively unimpaired people.

CONCLUSION

The emerging evidence from biomarker and clinical studies suggests MBI can be an early manifestation of underlying neurodegenerative disease. Future research must now further validate MBI to improve identification of those at the very earliest stages of disease.

Neuropsychiatric symptoms and cerebrovascular risk in non-demented elders: cross-sectional study using the mild behavioural impairment checklist (MBI-C)

BACKGROUND

Neuropsychiatric symptoms (NPS) may represent early clinical manifestations of evolving brain diseases. Studies underpin the occurrence of NPS in the context of mild cognitive impairment (MCI) and prodromal Alzheimer's disease, where symptoms referred to as 'mild behavioural impairment' (MBI) have been shown to predict conversion to dementia and to hasten cognitive/functional decline. However, the association between NPS and cerebrovascular risk factors has been poorly investigated, despite the high prevalence of the latter among individuals with MCI. The aim of the present study was to investigate the association between MBI and cerebrovascular risk in a clinical sample of non-demented elders.

METHODS

Sixty-five MCI and 15 cognitively unimpaired older adults were cross-sectionally assessed with the Mild Behavioural Impairment Checklist (MBI-C), using the cut-off score > 6.5 to define positive screening. Participants were submitted to the Hachinski Ischaemic Score (HIS) to account for cerebrovascular symptoms, vascular risk, and related comorbidities. Neuroimaging scans (magnetic resonance imaging and/or 18F-fluorodeoxyglucose-positron emission tomography) and apolipoprotein E genotype were obtained.

RESULTS

Positive associations were found between total MBI-C scores and increasing number of comorbidities present (0-2 comorbidities), but not with three comorbidities. Two domains of the MBI-C-impulse dyscontrol and social inappropriateness-followed the same trend of the MBI-C total score, with higher scores with the increasing numbers of comorbidities. No significant associations were found between MBI symptoms and HIS or cerebrovascular burden in neuroimaging assessment.

CONCLUSION

We found weak associations between MBI-C total score and the presence of comorbidities with cerebrovascular risk, but not with structural or functional neuroimaging abnormalities or HIS. This finding may represent that the presence of comorbidities adds limited risk to the occurrence of MBI in this sample of non-demented elders.

Neural Correlates of Mild Behavioral Impairment: A Functional Brain Connectivity Study Using Resting-State Functional Magnetic Resonance Imaging

Background:

Mild behavioral impairment (MBI) is associated with accelerated cognitive decline and greater risk of dementia. However, the neural correlates of MBI have not been completely elucidated.

Objective:

The study aimed to investigate the correlation between cognitively normal participants and participants with amnestic mild cognitive impairment (aMCI) using resting-state functional magnetic resonance imaging.

Methods:

The study included 30 cognitively normal participants and 13 participants with aMCI (20 men and 23 women; mean age, 76.9 years). The MBI was assessed using the MBI checklist (MBI-C). Region of interest (ROI)-to-ROI analysis was performed to examine the correlation between MBI-C scores and functional connectivity (FC) of the default mode network, salience network, and frontoparietal control network (FPCN). Age, Mini-Mental State Examination score, sex, and education were used as covariates. A p-value of 0.05, with false discovery rate correction, was considered significant.

Results:

A negative correlation was observed between the MBI-C total score and FC of the left posterior parietal cortex with the right middle frontal gyrus. A similar result was obtained for the MBI-C affective dysregulation domain score.

Conclusion:

FPCN dysfunction was detected as a neural correlate of MBI, especially in the affective dysregulation domain. This dysfunction may be associated with cognitive impairment in MBI and conversion of MBI to dementia; however, further longitudinal data are needed to examine this relationship.

Mild Behavioral Impairment Is Associated With Atrophy of Entorhinal Cortex and Hippocampus in a Memory Clinic Cohort

Objectives

Mild behavioral impairment (MBI) is a syndrome describing late-onset persistent neuropsychiatric symptoms (NPS) in non-demented older adults. Few studies to date have investigated the associations of MBI with structural brain changes. Our aim was to explore structural correlates of NPS in a non-demented memory clinic sample using the Mild Behavioral Impairment Checklist (MBI-C) that has been developed to measure MBI.

Methods

One hundred sixteen non-demented older adults from the Czech Brain Aging Study with subjective cognitive concerns were classified as subjective cognitive decline (n = 37) or mild cognitive impairment (n = 79). Participants underwent neurological and neuropsychological examinations and brain magnetic resonance imaging (MRI) (1.5 T). The Czech version of the MBI-C was administered to participants’ informants. Five a priori selected brain regions were measured, namely, thicknesses of the orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), posterior cingulate cortex (PCC), and entorhinal cortex (ERC) and volume of the hippocampus (HV), and correlated with MBI-C total and domain scores.

Results

Entorhinal cortex was associated with MBI-C total score (r_S = −0.368, p < 0.001) and with impulse dyscontrol score (r_S = −0.284, p = 0.002). HV was associated with decreased motivation (r_S = −0.248, p = 0.008) and impulse dyscontrol score (r_S = −0.240, p = 0.011).

Conclusion

Neuropsychiatric symptoms, particularly in the MBI impulse dyscontrol and motivation domains, are associated with medial temporal lobe atrophy in a clinical cohort of non-demented older adults. This study supports earlier involvement of temporal rather than frontal regions in NPS manifestation. Since these regions are typically affected early in the course of Alzheimer’s disease (AD), the MBI-C may potentially help further identify individuals at-risk of developing AD dementia.

Mild Behavioral Impairment and Subjective Cognitive Decline Predict Cognitive and Functional Decline

BACKGROUND

Mild behavioral impairment (MBI) and subjective cognitive decline (SCD) are dementia risk states, and potentially represent neurobehavioral and neurocognitive manifestations, respectively, of early stage neurodegeneration. Both MBI and SCD predict incident cognitive decline and dementia, are associated with known dementia biomarkers, and are both represented in the NIA-AA research framework for AD in Stage 2 (preclinical disease).

OBJECTIVE

To assess the associations of MBI and SCD, alone and in combination, with incident cognitive and functional decline in a population of older adults. We tested the hypothesis that MBI and SCD confer additive risk for decline.

METHODS

Cognitively normal participants were followed up annually at Alzheimer's Disease Centers. Logistic regression assessed the relationship between baseline classification (MBI-SCD-, MBI-SCD+, MBI+SCD-, or MBI+SCD+) and 3-year outcome.

RESULTS

Of 2,769 participants (mean age=76), 1,536 were MBI-SCD-, 254 MBI-SCD+, 743 MBI+SCD-, and 236 MBI+SCD+. At 3 years, 349 (12.6%) declined to CDR >0, including 23.1% of the MBI+group, 23.5% of the SCD+group, and 30.9% of the intersection group of both MBI+and SCD+participants. Compared to SCD-MBI-, we observed an ordinal progression in risk (ORs [95% CI]): 3.61 [2.42-5.38] for MBI-SCD+ (16.5% progression), 4.76 [3.57-6.34] for MBI+SCD- (20.7%), and 8.15 [5.71-11.64] for MBI+SCD+(30.9%).

CONCLUSION

MBI and SCD together were associated with the greatest risk of decline. These complementary dementia risk syndromes can be used as simple and scalable methods to identify high-risk patients for workup or for clinical trial enrichment.