Dementia: diagnosis and evaluation

Primary Care Pracitioner Perspectives on the Role of Primary Care in Dementia Diagnosis and Care

Importance

Although the barriers to dementia care in primary care are well characterized, primary care practitioner (PCP) perspectives could be used to support the design of values-aligned dementia care pathways that strengthen the role of primary care.

Objective

To describe PCP perspectives on their role in dementia diagnosis and care.

Design, Setting, and Participation

In this qualitative study, interviews were conducted with 39 PCPs (medical doctors, nurse practitioners, and doctors of osteopathic medicine) in California between March 2020 and November 2022. Results were analyzed using thematic analysis.

Main Outcomes and Measures

Overarching themes associated with PCP roles in dementia care.

Results

Interviews were conducted with 39 PCPs (25 [64.1%] were female; 16 [41%] were Asian). The majority (36 PCPs [92.3%]) reported that more than half of their patients were insured via MediCal, the California Medicaid program serving low-income individuals. Six themes were identified that convey PCPs' perspectives on their role in dementia care. These themes focused on (1) their role as first point of contact and in the diagnostic workup; (2) the importance of long-term, trusting relationships with patients; (3) the value of understanding patients' life contexts; (4) their work to involve and educate families; (5) their activities around coordinating dementia care; and (6) how the care they want to provide may be limited by systems-level constraints.

Conclusions and Relevance

In this qualitative study of PCP perspectives on their role in dementia care, there was alignment between PCP perspectives about the core values of primary care and their work diagnosing and providing care for people living with dementia. The study also identified a mismatch between these values and the health systems infrastructure for dementia care in their practice environment.

Conventional Synthetic Disease-Modifying Anti-Rheumatic Drugs and the Risk of Vascular Dementia in Patients with Spondyloarthritis: A Database Cohort Study

Axial spondyloarthritis (axSpA) is a chronic inflammatory rheumatic disease that mainly affects the axial bones, and dementia is characterized by a decline in cognitive function, leading to dependence in everyday activity. Although the association between dementia and ankylosing spondylitis has been investigated, the influence of axSpA medication on dementia risk is unclear. The aim of this study was to investigate the risk of dementia among axSpA patients and if the conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs) can reduce the risk of dementia. Patients with axSpA whose data were recorded during 2004-2008 and who were followed up until the end of 2010 were recruited. A control cohort was matched by age and sex. A Cox multivariate proportional hazards model was applied to analyze the risk factors for dementia. The hazard ratio (HR) and adjusted HR (aHR) were estimated between the study and control cohorts. The effects of csDMARDs and steroid use on the risk of different types of dementia were also analyzed. In total, 2341 and 11,705 patients constituted the axSpA and control cohort, respectively. The axSpA cohort had a greater risk of vascular dementia (aHR = 2.09 (1.36-3.20). The risk of dementia (aHR = 1.01 (0.55-1.85) did not significantly differ between patients with axSpA who received csDMARDs. In conclusion, patients with axSpA are at a risk of vascular dementia, which could be reduced by csDMARDs.

The influence of stimulus eccentricity on prosaccade outcomes in patients with Alzheimer's Disease dementia at an early stage and amnestic mild cognitive impairment

INTRODUCTION

Prosaccade task is a widely used objective method to evaluate reflexive saccade and visual attention. The study aimed to investigate prosaccade stimulus eccentricity, compare prosaccade parameters in patients with Alzheimer's disease dementia (AD), amnestic mild cognitive impairment (aMCI), and neurotypical adults (NA), and examine the relationship between prosaccade and neuropsychological tests.

METHODS

Thirty patients with AD, 34 with aMCI, and 32 NA were included in the study. Eye movements were recorded with the EyeLink 1000 Plus in the prosaccade task, and this study evaluated cognitive function with comprehensive neuropsychological tests assessing attention, memory, executive function, visuospatial function, and language domains.

RESULTS

The correct saccade rates of patients with AD were significantly lower than NA in the 5^° and 10^° stimulus eccentricities. Patients with AD had significantly longer latencies in the 10° stimulus eccentricity than those with aMCI and NA. Patients with aMCI did not differ in prosaccade performance compared to NA. Prosaccade parameters were significantly correlated with all cognitive domains. As the amplitude of the stimuli increased, the rate of correct saccades decreased, while the express saccade rate, latency, amplitude, and peak velocity increased.

CONCLUSION

Our findings that correct saccade rates and latency may be distinguishing parameters of early AD are promising. This study also found that stimulus eccentricity affects prosaccade measures in AD, MCI, and NA.

Dysfunction of the Blood-Brain Barrier-A Key Step in Neurodegeneration and Dementia

The vascular endothelium in the brain is an essential part of the blood-brain-barrier (BBB) because of its very tight structure to secure a functional and molecular separation of the brain from the rest of the body and to protect neurons from pathogens and toxins. Impaired transport of metabolites across the BBB due to its increasing dysfunction affects brain health and cognitive functioning, thus providing a starting point of neurodegenerative diseases. The term “cerebral metabolic syndrome” is proposed to highlight the importance of lifestyle factors in neurodegeneration and to describe the impact of increasing BBB dysfunction on neurodegeneration and dementia, especially in elderly patients. If untreated, the cerebral metabolic syndrome may evolve into dementia. Due to the high energy demand of the brain, impaired glucose transport across the BBB via glucose transporters as GLUT1 renders the brain increasingly susceptible to neurodegeneration. Apoptotic processes are further supported by the lack of essential metabolites of the phosphocholine synthesis. In Alzheimer’s disease (AD), inflammatory and infectious processes at the BBB increase the dysfunction and might be pace-making events. At this point, the potentially highly relevant role of the thrombocytic amyloid precursor protein (APP) in endothelial inflammation of the BBB is discussed. Chronic inflammatory processes of the BBB transmitted to an increasing number of brain areas might cause a lasting build-up of spreading, pore-forming β-amyloid fragments explaining the dramatic progression of the disease. In the view of the essential requirement of an early diagnosis to investigate and implement causal therapeutic strategies against dementia, brain imaging methods are of great importance. Therefore, status and opportunities in the field of diagnostic imaging of the living human brain will be portrayed, comprising diverse techniques such as positron emissions tomography (PET) and functional magnetic resonance imaging (fMRI) to uncover the patterns of atrophy, protein deposits, hypometabolism, and molecular as well as functional alterations in AD.

Brief Cognitive Tests in the Case of Dementia and Alzheimer's Disease Early Diagnosis

Nowadays, Alzheimer's disease (AD) diagnosis is considered to be a crucial and extremely complex process. Nevertheless, psychometric tools, like Mini-Mental State Evaluation (MMSE), are used to address cognitive function assessment and clinical evaluation processes. However, MMSE's sensitivity in the diagnosis of mild cognitive impairment is debatable in terms of education, age, or nationality. Typical psychometric tools with the use of "paper and pencil" methods combined with physiology measurements are proposed in order to enhance validity and effectiveness in the case of Alzheimer's disease cognitive deficits. The objective of this review study is to highlight the effectiveness of brief cognitive tests (BCT) in the case of dementia and Alzheimer's disease screening. Authors' future work will focus on the application of BCT in MCI diagnosis and evaluation.

Progression of Alzheimer's Disease by Self-Reported Cancer History in the Alzheimer's Disease Neuroimaging Initiative

BACKGROUND

Cross-sectional studies suggest self-reported cancer history is associated with decreased risk of Alzheimer's disease (AD). However, little is known about how self-reported cancer affects longitudinal AD progression, the primary outcome in clinical trials and observational studies.

OBJECTIVE

To determine self-reported cancer history's effect on longitudinal AD progression in an observational study.

METHODS

We utilized data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) to evaluate progression to AD by self-reported all-cancer, breast, prostate, colorectal, or non-melanoma skin cancer history. Linear mixed effects models were used to examine baseline differences and rates of progression on the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) by self-reported cancer history. Age at AD onset was examined using consensus clinical diagnoses with Cox proportional hazards regression.

RESULTS

Among 1,271 participants, models revealed no significant differences in progression over time but did reveal significantly lower baseline ADAS-Cog score, indicating better cognition at a given age in those with self-reported cancer history. Cox models indicated those with self-reported cancer history had significantly later age of AD onset (HR: 0.67, 95% CI: 0.53-0.85) after adjustment for covariates.

CONCLUSION

Participants with self-reported cancer history entered ADNI with better cognition and later age of AD onset, but progressed similarly to participants without such history, indicating differences in AD between those with and without self-reported cancer history emerge early in the disease course. Such differences in longitudinal progression by self-reported cancer history could affect AD trials and observational studies, given the current focus on early disease course. Further investigation is warranted with detailed longitudinal assessment of cancer and AD.

Mesenchymal Stromal Cell Therapies for Neurodegenerative Diseases

Mesenchymal stromal cells are multipotent cells that are being used to treat a variety of medical conditions. Over the past decade, there has been considerable excitement about using MSCs to treat neurodegenerative diseases, which are diseases that are typically fatal and without other robust therapies. In this review, we discuss the proposed MSC mechanisms of action in neurodegenerative diseases, which include growth factor secretion, exosome secretion, and attenuation of neuroinflammation. We then provide a summary of preclinical and early clinical work on MSC therapies in amyotrophic lateral sclerosis, multiple system atrophy, Parkinson disease, and Alzheimer disease. Continued rigorous and controlled studies of MSC therapies will be critical in order to establish efficacy and protect patients from possible untoward effects.

Increased Risk of Dementia in Patients With Systemic Lupus Erythematosus: A Nationwide Population-Based Cohort Study

OBJECTIVE

Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder characterized by varied clinical symptoms and can be comorbid with neuropsychiatric disorders. However, the association between SLE and dementia risk in patients with SLE remains unclear. In this study, we evaluated the incidence of dementia in patients with SLE.

METHODS

Patients were recruited from a nationwide cohort in 2004-2008 and categorized as SLE (n = 1,074; patients diagnosed with SLE) or non-SLE (n = 5,370; age- and sex-matched controls). Each patient was followed for up to 7 years, until either receiving a diagnosis of dementia or until December 31, 2010. Data were analyzed using the Kaplan-Meier method and Cox regression analysis.

RESULTS

The incidence rate of dementia was higher in the SLE cohort (357 per 100,000 person-years) than in the non-SLE cohort (180 per 100,000 person-years). Patients with SLE had a higher risk of dementia than did those without SLE (crude hazard ratio [HR] 1.92; P < 0.05). Cox regression analysis revealed an adjusted HR for dementia in the SLE cohort of 2.14 (P < 0.001), after adjustment for other comorbid diseases and variables.

CONCLUSION

Patients with SLE have a higher risk of dementia.

Risk of Dementia in Patients with Spinal Cord Injury: A Nationwide Population-Based Cohort Study

Spinal cord injury (SCI) can cause physical disability and psychological distress; however, whether SCI is a risk factor for dementia is unclear. This study evaluated the incidence of dementia in patients with SCI. Study participants were recruited from a nationwide cohort during 2004-2007 and categorized into SCI (patients diagnosed with SCI; n = 941) and non-SCI (age- and sex-matched controls; n = 5060) cohorts. Each participant was followed for 7 years until diagnosis of dementia or December 31, 2010, whichever occurred first. Data were subjected to Kaplan-Meier and Cox regression analyses. The incidence of dementia was significantly higher in the SCI cohort (1106 per 100,000 person-years) than in the non-SCI cohort (p < 0.001). Patients with SCI had a significantly higher risk of dementia than did those without SCI (crude hazard ratio [HR] = 2.14, 95% confidence interval [CI], 1.57-2.92, p < 0.001 vs. adjusted HR = 1.95, 95% CI, 1.43-2.67, p < 0.001). Further analysis found that there is no statistical significance of higher risk for developing Alzheimer's disease among SCI patients, but that SCI patients were at higher risk of developing other types of dementia than the control cohort (crude HR = 1.88, 95% CI, 1.33-2.63, p < 0.001 vs. adjusted HR = 1.90, 95% CI, 1.35-2.68, p < 0.001). In conclusion, patients with SCI are at high risk of dementia, and effective dementia prevention strategies are recommended for comprehensive SCI care.

Nanotechnology-based drug delivery systems for the treatment of Alzheimer's disease

Alzheimer's disease is a neurological disorder that results in cognitive and behavioral impairment. Conventional treatment strategies, such as acetylcholinesterase inhibitor drugs, often fail due to their poor solubility, lower bioavailability, and ineffective ability to cross the blood-brain barrier. Nanotechnological treatment methods, which involve the design, characterization, production, and application of nanoscale drug delivery systems, have been employed to optimize therapeutics. These nanotechnologies include polymeric nanoparticles, solid lipid nanoparticles, nanostructured lipid carriers, microemulsion, nanoemulsion, and liquid crystals. Each of these are promising tools for the delivery of therapeutic devices to the brain via various routes of administration, particularly the intranasal route. The objective of this study is to present a systematic review of nanotechnology-based drug delivery systems for the treatment of Alzheimer's disease.

Cohort study evaluating the risk of hip fracture among patients with dementia in Taiwan

BACKGROUND

To investigate the incidence and risk of hip fracture among dementia patients

METHODS

This is a retrospective population-based 7-year cohort study using case-control matched analysis database from Taiwan's Longitudinal Health Insurance Database 2005. Patients were diagnosed with codes or International Classification of Diseases-9-CM codes of dementia, between 1 January 2004 and 31 December 2006. The prevalence and the adjusted odds ratio of hip fracture among dementia patients and the controls were estimated.

RESULTS

We enrolled 3101 patients with dementia in the dementia cohort and 12,404 (1:4) patients in the control group. Of these, 202 patients experienced hip fractures. The incidence of hip fracture was 1178 per 100,000 person-years in the dementia cohort and 624 per 100,000 person-years in the comparison cohort. The hip fracture hazard ratio during the follow-up period was 1.89 (95% confidence interval [CI] 1.60-2.23, p < 0.001) for dementia patients. After adjusting for the covariates, the hazard ratio of hip fracture was 1.41 (95% CI, 1.19-1.69, p < 0.001) for dementia patients.

CONCLUSION

People with dementia experience an increased incidence of hip fracture and are at a higher risk of sustaining a hip fracture in the future. Proper and effective hip fracture-prevention strategies are essential for dementia patients.

RIG-1 receptor expression in the pathology of Alzheimer's disease

BACKGROUND

Neuroinflammation plays a critical role in the pathogenesis of Alzheimer's disease (AD) and involves activation of the innate immune response via recognition of diverse stimuli by pattern recognition receptors (PRRs). The inflammatory inducers and precise innate signaling pathway contributing to AD pathology remain largely undefined.

RESULTS

In the present study we analyzed expression levels of innate immune proteins in temporal and occipital cortices from preclinical (no cognitive impairment, NCI, N = 22) to mild cognitive impairment (MCI, N = 20) associated with AD pathology (N = 20) and AD patients (N = 23). We found that retinoic acid-inducible gene-I (RIG-1) is significantly elevated in the temporal cortex and plasma in patients with MCI. In addition, primary human astrocytes stimulated with the RIG-1 ligand 5'ppp RNA showed increased expression of amyloid precursor protein (APP) and amyloid-β (Aβ), supporting the idea that RIG-1 is involved in the pathology of MCI associated with early progression to AD.

CONCLUSION

These findings suggest that RIG-1 may play a critical role in incipient AD.

Late life psychosis: assessment and general treatment strategies

With the increased number of elderly patients suffering from mental illness, an increased incidence of psychiatric conditions including psychotic disorders is also expected. When psychosis occurs in the elderly, its assessment and treatment may pose a challenge for primary care clinicians and caregivers. This article will review the assessment and treatment of late life psychosis.

Alzheimer's disease and mild cognitive impairment

As our society ages, age-related diseases assume increasing prominence as both personal and public health concerns. Disorders of cognition are particularly important in both regards, and Alzheimer's disease is by far the most common cause of dementia of aging. In 2000, the prevalence of Alzheimer's disease in the United States was estimated to be 4.5 million individuals, and this number has been projected to increase to 14 million by 2050. Although not an inevitable consequence of aging, these numbers speak to the dramatic scope of its impact. This article focuses on Alzheimer's disease and the milder degrees of cognitive impairment that may precede the clinical diagnosis of probable Alzheimer's disease, such as mild cognitive impairment.

Impaired physical performance and the assessment of dementia of the Alzheimer type

CONTEXT

Impaired physical performance may confound the clinical assessment of dementia of the Alzheimer type (DAT).

OBJECTIVES

Determine whether: (1) Physical Performance Test (PPT) scores are associated with the Clinical Dementia Rating (CDR), (2) PPT scores are correlated with clinical measures of health, and (3) impaired physical performance affects the clinical assessment of DAT.

DESIGN

A retrospective and cross-sectional study.

SETTING

An Alzheimer's Disease Research Center.

PARTICIPANTS

Ninety-nine research volunteers aged 85 years and older were assessed from September 1997 through July 1999; 45 had DAT (CDR = 0.5-2), and 54 were nondemented controls.

MEASUREMENTS

Clinical health history, daily functioning, physical and neurologic status, CDR, sum of boxes, and total PPT score were obtained during clinical evaluation. Independently assessed psychometric measures of verbal and nonverbal episodic and semantic memory, visuospatial abilities, and psychometric speed yielded to a factor score representing general cognitive function. Our outcome measure was the CDR (ie, the clinical dementia rating, where higher scores indicate greater dementia severity).

RESULTS

The majority (88%) of subjects in this sample of demented and nondemented older adults had some degree of physical impairment as measured by the PPT. Correlational analyses identified clinically important relationships (/taub/ > 0.30, p < 0.05) between impaired PPT performance, higher CDR rating, and poor general health, including difficulty ambulating. The correlation between PPT performance and dementia severity (taub = -0.36) decreased after controlling for cognitive ability (taub = -0.19). The correlation between the cognitive factor score and dementia severity when PPT performance was controlled (taub = -0.60) was similar to the unadjusted correlation of the factor score with dementia severity (taub = -0.64).

CONCLUSIONS

The presence of some degree of physical impairment was common in our sample, and PPT scores correlated with both physical and cognitive impairment. Nevertheless, Alzheimer Disease Research Center clinicians appear able to successfully distinguish between physical and cognitive causes of functional impairment and assign a CDR rating that accurately reflects DAT severity in individuals with impaired physical performance.

Essentials of the proper diagnoses of mild cognitive impairment, dementia, and major subtypes of dementia

Loss of cognitive function in the elderly population is a common condition encountered in general medical practice. Diagnostic criteria and approaches have become more refined and explicit in the past several years. Precise diagnosis is feasible clinically. In this article, the precursor state and major subtypes of dementia are considered. Mild cognitive impairment is the term given to patients with cognitive impairment that is detectable by clinical criteria but does not produce impairment in daily functioning. When daily functioning is impaired as a result of cognitive decline, dementia is the appropriate syndromic label. Specific causes of dementia tend to have distinctive clinical presentations: the anterograde amnesic syndrome of Alzheimer disease; the syndrome of dementia with cerebrovascular disease; the syndrome of Lewy body dementia with its distinctive constellation of extrapyramidal features, disordered arousal, and dementia; the behavioral-cognitive syndrome of frontotemporal dementia; the primary progressive aphasias; and the rapidly progressive dementias. Because dementia syndromes have distinctive natural histories, precise diagnosis leads to a better understanding of prognosis. As new treatments become available for Alzheimer disease, the most common of the dementias, accurate diagnosis allows the appropriate patients to receive treatment.

The recognition, assessment and management of dementing disorders: conclusions from the Canadian Consensus Conference on Dementia

OBJECTIVE

i) To develop evidence based consensus statements on which to build clinical practice guidelines for primary care physicians towards the recognition, assessment and management of dementing disorders; ii) to disseminate and evaluate the impact of these statements and guidelines built on these statements.

OPTIONS

Structured approach to assessment, including recommended laboratory tests, choices for neuroimaging and referral; management of complications (especially behaviour problems and depression) and use of cognitive enhancing agents. POTENTIAL OUTCOMES: Consistent and improved clinical care of persons with dementia; cost containment by more selective use of laboratory investigations, neuroimaging and referrals; appropriate use of cognitive enhancing agents.

EVIDENCE

Authors of each background paper were entrusted to: perform a literature search, discover additional relevant material including references cited in retrieved articles; consult with other experts in the field and then synthesize information. Standard rules of evidence were applied. Based upon this evidence, consensus statements were developed by a group of experts, guided by a steering committee of eight individuals from the areas of Neurology, Geriatric Medicine, Psychiatry, Family Medicine, Preventive Health Care and Health Care Systems.

VALUES

Recommendations have been developed with particular attention to the context of primary care and are intended to support family physicians in their ongoing assessment and care of patients with dementia.

BENEFITS, HARMS AND COSTS

Potential for improved clinical care of individuals with dementia. A dissemination and evaluation strategy will attempt to measure the impact of the recommendations.

RECOMMENDATIONS

See text.

VALIDATION

Four other sets of consensus statements and/or guidelines have been published recently. These recommendations are generally congruent with our own consensus statements. The consensus statements have been endorsed by relevant bodies in Canada.

Magnetic resonance imaging and magnetic resonance spectroscopy in dementias

This article reviews recent studies of magnetic resonance imaging and magnetic resonance spectroscopy in dementia, including Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, idiopathic Parkinson's disease, Huntington's disease, and vascular dementia. Magnetic resonance imaging and magnetic resonance spectroscopy can detect structural alteration and biochemical abnormalities in the brain of demented subjects and may help in the differential diagnosis and early detection of affected individuals, monitoring disease progression, and evaluation of therapeutic effect.

Aging, mild cognitive impairment, and Alzheimer's disease

Research in the field of aging and dementia is moving forward at a rapid pace, in both basic biology of dementing disorders and clinical investigations. These two approaches to research on aging and dementia need to advance in parallel, such that when work on the pathophysiology of these disorders is translated into therapeutic practice, the appropriately characterized clinical cohorts will be available for therapeutic trials of these treatment strategies.

Beyond the Folstein: dementia in primary care

As the population of elderly patients continues to increase world-wide, the importance of identifying patients with dementia in primary care practices will increase. Our ability to see patients for an extended period of time may enable primary care physicians to identify patients with dementia early in their disease process. This enables patients, families, and caregivers to initiate treatment early, with the hope that future research will identify successful treatment modalities. This article discusses the identification of dementing syndromes, the importance of identifying familial needs and coping strategies, and the importance of caregiver stress.

Frequently missed diagnosis in geriatric psychiatry

Older adults are an important segment of the population that has specific health care needs. Their unique biopsychosocial characteristics impact the presentation, evaluation, and management of psychiatric illnesses. This article describes how common psychiatric disorders present in an aging population. Research in this area is relatively new and much more information is still needed. Close attention should be paid to new knowledge as it emerges about this growing population.

Senile chorea: a multicenter prospective study

Senile chorea (SC) is characterized by the presence of late onset, generalized chorea with no family history and no dementia. It is unclear whether it is a distinct clinical entity or represents late onset Huntington's disease (HD) with an undetected family history. In order to clarify this issue, we carried out a prospective, multicenter study of suspected cases of SC. Since 1994 we identified six cases that met clinical criteria for SC. Their study included routine lab tests, cerebral MRI, neuropsychological assessment, and lastly gene IT15 analysis. An abnormal expansion of the (CAG)n repeat was found in three patients. Although there were no criteria for dementia, most neuropsychological tests revealed mild to moderate deficits, particularly in visuospatial and prefrontal tasks, m all six patients, those that were finally diagnosed as having late onset "sporadic" HD, but also in patients that finally had SC. This study provides further evidence on the existence of SC; however, the distinction from late onset "sporadic" HD seems not to be possible on clinical grounds unless a genetic study is carried out. Some cases of suspected "SC" have late onset "sporadic" HD.

Geriatric health maintenance

OBJECTIVE

To highlight articles pertaining to geriatric health maintenance and provide clinicians with current evidence supportive of or opposed to screening or treatment for various diseases and conditions.

METHOD

We conducted a computer-assisted search of the relevant medical literature and summarized the results of pertinent studies in the elderly population.

RESULTS

The geriatric population is progressively increasing in numbers. Unfortunately, no consensus exists about health maintenance in this population. To date, the United States Preventive Services Task Force has made several recommendations about preventive services; however, they did not specifically focus on the geriatric age-group. We outline their guidelines and discuss our clinical practices in a wide variety of encounters with geriatric patients.

CONCLUSION

The efficacy of many screening tests and interventions for preventing illness in elderly patients is unclear. As the general population continues to age, further research in this area will be important.

Cobalamin

Cobalamin (vitamin B12) is an essential nutrient derived exclusively from bacterial sources. It is an essential cofactor for three known enzymatic reactions. Untreated deficiency, caused by either the autoimmune disease pernicious anemia or nutritional lack, results in a macrocytic anemia and/or subacute combined degeneration of the spinal cord and is eventually fatal. Cobalamin in serum is bound to two proteins, transcobalamin and haptocorrin. The former is responsible for the essential delivery of cobalamin to most tissues. Inadequate tissue availability of cobalamin results in increased concentration of methylmalonic acid and homocyst(e)ine due to inhibition of methylmalonyl-CoA mutase and methionine synthase, respectively. Strict vegetarians have long been known to be at risk of cobalamin deficiency, which develops insidiously over many years. It is now clear that a significant number of the elderly and HIV-positive individuals are also at increased risk of deficiency. Any individual with reduced ability to split cobalamin from food-protein may also become deficient even though intrinsic factor is present. Diagnosis of cobalamin deficiency has frequently relied on total serum cobalamin and the Schilling test. Newer approaches such as analysis of methylmalonic acid, homocyst(e)ine, holotranscobalamin, anti-intrinsic factor antibodies, and serum gastrin may provide more cost-effective testing, as well as identify those with a covert deficiency.