Critical review of the Appropriate Use Criteria for amyloid imaging: Effect on diagnosis and patient care

Computerized decision support is an effective approach to select memory clinic patients for amyloid-PET

BACKGROUND

The use of amyloid-PET in dementia workup is upcoming. At the same time, amyloid-PET is costly and limitedly available. While the appropriate use criteria (AUC) aim for optimal use of amyloid-PET, their limited sensitivity hinders the translation to clinical practice. Therefore, there is a need for tools that guide selection of patients for whom amyloid-PET has the most clinical utility. We aimed to develop a computerized decision support approach to select patients for amyloid-PET.

METHODS

We included 286 subjects (135 controls, 108 Alzheimer's disease dementia, 33 frontotemporal lobe dementia, and 10 vascular dementia) from the Amsterdam Dementia Cohort, with available neuropsychology, APOE, MRI and [18F]florbetaben amyloid-PET. In our computerized decision support approach, using supervised machine learning based on the DSI classifier, we first classified the subjects using only neuropsychology, APOE, and quantified MRI. Then, for subjects with uncertain classification (probability of correct class (PCC) < 0.75) we enriched classification by adding (hypothetical) amyloid positive (AD-like) and negative (normal) PET visual read results and assessed whether the diagnosis became more certain in at least one scenario (PPC≥0.75). If this was the case, the actual visual read result was used in the final classification. We compared the proportion of PET scans and patients diagnosed with sufficient certainty in the computerized approach with three scenarios: 1) without amyloid-PET, 2) amyloid-PET according to the AUC, and 3) amyloid-PET for all patients.

RESULTS

The computerized approach advised PET in n = 60(21%) patients, leading to a diagnosis with sufficient certainty in n = 188(66%) patients. This approach was more efficient than the other three scenarios: 1) without amyloid-PET, diagnostic classification was obtained in n = 155(54%), 2) applying the AUC resulted in amyloid-PET in n = 113(40%) and diagnostic classification in n = 156(55%), and 3) performing amyloid-PET in all resulted in diagnostic classification in n = 154(54%).

CONCLUSION

Our computerized data-driven approach selected 21% of memory clinic patients for amyloid-PET, without compromising diagnostic performance. Our work contributes to a cost-effective implementation and could support clinicians in making a balanced decision in ordering additional amyloid PET during the dementia workup.

Trajectory of clinical symptoms in relation to amyloid chronicity

Introduction

While it is generally appreciated that amyloid precedes symptomatic Alzheimer's disease (AD) by decades, a greater understanding of this timeline may increase prognostic accuracy, planning, and care of persons who are on the AD continuum.

Methods

We examined trajectories of Clinical Dementia Rating-Sum of Boxes (CDR-SB) relative to estimated years of amyloid positivity (A+) in n = 123 participants who were all A+ based on [C-11]Pittsburgh compound B positron emission tomography.

Results

The average amyloid chronicity at CDR-SB of 2.5 was 20.1 years. The average trajectory of CDR-SB accelerated after 10 years of elevated amyloid and varied greatly between 10 and 30 years. Exploratory analyses suggested that older age and higher volume of white matter hyperintensities shortened the interval between amyloid onset and cognitive impairment.

Discussion

The recontextualization of amyloid burden into the time domain will facilitate studies of disease progression, the influence of co-pathology, and factors that hasten or slow cognitive impairment.

Amyloid PET ordering practices in a memory disorders clinic

Introduction

This study assessed the ordering of amyloid positron emission tomography (PET) scans in a Veterans Affairs (VA) memory disorders clinic as part of routine clinical care, with possible implications for the extent to which ordering may occur outside of the VA in the future if covered by insurance.

Methods

Clinical features predictive of ordering amyloid PET scans were retrospectively assessed; the percentage of patients who met appropriate use criteria were evaluated.

Results

Among 565 veterans, 34.9% of received an amyloid PET scan and 98.0% of these were consistent with appropriate use criteria. Patients with a PET were younger and more likely to have an initial diagnosis of Alzheimer's disease (AD). Of patients without an amyloid PET scan ordered, 64.4% would have met appropriate use criteria for amyloid PET.

Discussion

The majority of scans ordered were consistent with appropriate use criteria and more patients were eligible than received a scan. The current study's findings that approximately one-third of patients in a memory disorders clinic received an amyloid PET scan has implications for memory disorders clinics inside and outside of the US Veterans Health Administration.

[18F]THK-5351 PET Patterns in Patients With Alzheimer's Disease and Negative Amyloid PET Findings

Background and Purpose

Alzheimer’s disease (AD) does not always mean amyloid positivity. [¹⁸F]THK-5351 has been shown to be able to detect reactive astrogliosis as well as tau accompanied by neurodegenerative changes. We evaluated the [¹⁸F]THK-5351 retention patterns in positron-emission tomography (PET) and the clinical characteristics of patients clinically diagnosed with AD dementia who had negative amyloid PET findings.

Methods

We performed 3.0-T magnetic resonance imaging, [¹⁸F]THK-5351 PET, and amyloid PET in 164 patients with AD dementia. Amyloid PET was visually scored as positive or negative. [¹⁸F]THK-5351 PET were visually classified as having an intratemporal or extratemporal spread pattern.

Results

The 164 patients included 23 (14.0%) who were amyloid-negative (age 74.9±8.3 years, mean±standard deviation; 9 males, 14 females). Amyloid-negative patients were older, had a higher prevalence of diabetes mellitus, and had better visuospatial and memory functions. The frequency of the apolipoprotein E ε4 allele was higher and the hippocampal volume was smaller in amyloid-positive patients. [¹⁸F]THK-5351 uptake patterns of the amyloid-negative patients were classified into intratemporal spread (n=10) and extratemporal spread (n=13). Neuropsychological test results did not differ significantly between these two groups. The standardized uptake value ratio of [¹⁸F]THK-5351 was higher in the extratemporal spread group (2.01±0.26 vs. 1.61±0.15, p=0.001). After 1 year, Mini Mental State Examination (MMSE) scores decreased significantly in the extratemporal spread group (-3.5±3.2, p=0.006) but not in the intratemporal spread group (-0.5±2.8, p=0.916). The diagnosis remained as AD (n=5, 50%) or changed to other diagnoses (n=5, 50%) in the intratemporal group, whereas it remained as AD (n=8, 61.5%) or changed to frontotemporal dementia (n=4, 30.8%) and other diagnoses (n=1, 7.7%) in the extratemporal spread group.

Conclusions

Approximately 70% of the patients with amyloid-negative AD showed abnormal [¹⁸F]THK-5351 retention. MMSE scores deteriorated rapidly in the patients with an extratemporal spread pattern.

Statistical Parametric Mapping in Amyloid Positron Emission Tomography

Alzheimer's disease (AD), the most common cause of dementia, has limited treatment options. Emerging disease modifying therapies are targeted at clearing amyloid-β (Aβ) aggregates and slowing the rate of amyloid deposition. However, amyloid burden is not routinely evaluated quantitatively for purposes of disease progression and treatment response assessment. Statistical Parametric Mapping (SPM) is a technique comparing single-subject Positron Emission Tomography (PET) to a healthy cohort that may improve quantification of amyloid burden and diagnostic performance. While primarily used in 2-[18F]-fluoro-2-deoxy-D-glucose (FDG)-PET, SPM's utility in amyloid PET for AD diagnosis is less established and uncertainty remains regarding optimal normal database construction. Using commercially available SPM software, we created a database of 34 non-APOE ε4 carriers with normal cognitive testing (MMSE > 25) and negative cerebrospinal fluid (CSF) AD biomarkers. We compared this database to 115 cognitively normal subjects with variable AD risk factors. We hypothesized that SPM based on our database would identify more positive scans in the test cohort than the qualitatively rated [11C]-PiB PET (QR-PiB), that SPM-based interpretation would correlate better with CSF Aβ42 levels than QR-PiB, and that regional z-scores of specific brain regions known to be involved early in AD would be predictive of CSF Aβ42 levels. Fisher's exact test and the kappa coefficient assessed the agreement between SPM, QR-PiB PET, and CSF biomarkers. Logistic regression determined if the regional z-scores predicted CSF Aβ42 levels. An optimal z-score cutoff was calculated using Youden's index. We found SPM identified more positive scans than QR-PiB PET (19.1 vs. 9.6%) and that SPM correlated more closely with CSF Aβ42 levels than QR-PiB PET (kappa 0.13 vs. 0.06) indicating that SPM may have higher sensitivity than standard QR-PiB PET images. Regional analysis demonstrated the z-scores of the precuneus, anterior cingulate and posterior cingulate were predictive of CSF Aβ42 levels [OR (95% CI) 2.4 (1.1, 5.1) p = 0.024; 1.8 (1.1, 2.8) p = 0.020; 1.6 (1.1, 2.5) p = 0.026]. This study demonstrates the utility of using SPM with a "true normal" database and suggests that SPM enhances diagnostic performance in AD in the clinical setting through its quantitative approach, which will be increasingly important with future disease-modifying therapies.

Clinical Impact of PET With 18F-FDG and 11C-PIB in Patients With Dementia in a Developing Country

Introduction: The objective of this study was to evaluate the clinical impact PET with ¹⁸F-FDG and ¹¹C-PIB in patients with dementia in a developing country.

Methodology: Retrospective study of the patients referred for the evaluation of dementia to the only PET center in Uruguay. A total of 248 patients were identified, from which 70 patients were included based on the availability of medical history and clinical follow-up. Main outcomes included change in diagnosis, diagnostic dilemma and AD treatment. We evaluated the association of clinical outcomes with PET concordance with baseline diagnosis, diagnostic dilemma, level of education, AD pathology/Non-AD pathology (AD/Non-AD), baseline diagnosis and ¹¹C-PIB PET result.

Results: Baseline clinical diagnosis was concordant with ¹⁸F-FDG and ¹¹C-PIB PET results in 64.7 and 77.1% of the patients, respectively. Change in diagnosis after PET was identified in 30.0% of the patients and was associated with discordant ¹⁸F-FDG (p = 0.002) and ¹¹C-PIB (p < 0.001) PET results, previous diagnostic dilemma (p = 0.005), low education (p = 0.027), Non-AD baseline diagnosis (p = 0.027), and negative ¹¹C-PIB PET result (p < 0.001). Only the last variable remained significant in the multivariate analysis (adjusted p = 0.038). Diagnostic dilemma decreased after PET from 15.7 to 7.1% (p = 0.11) and was associated with Non-AD diagnosis (p = 0.002) and negative ¹¹C-PIB PET result (p = 0.003). Change in AD treatment after PET occurred in 45.7% of the patients.

Conclusion:¹⁸F-FDG and ¹¹C-PIB PET had a significant clinical impact in terms of change in diagnosis and treatment in patients with dementia in a developing country, similar to that reported in high-income countries.

Advances in Brain Amyloid Imaging

Amyloid-β (Aβ) PET imaging has now been available for over 15 years. The ability to detect Aβ in vivo has greatly improved the clinical and research landscape of Alzheimer's disease (AD) and other neurodegenerative conditions. Aβ imaging provides very reliable, accurate, and reproducible measurements of regional and global Aβ burden in the brain. It has proved invaluable in anti-Aβ therapy trials, and is now recognized as a powerful diagnostic tool. The appropriate use of Aβ PET, when combined with comprehensive clinical evaluation by a dementia-trained specialist, can improve the accuracy of a clinical diagnosis of AD and substantially alter management. It can assist in differentiating AD from other neurodegenerative conditions, often by its ability to rule out the presence of Aβ. When combined with tau imaging, further increase in specificity for the diagnosis of AD can be achieved. The integration of Aβ PET, in conjunction with biomarkers of tau, neurodegeneration and neuroinflammation, into large, longitudinal, observational cohort studies continues to increase our understanding of the development of AD. Its incorporation into clinical trials has been pivotal in defining the most effective anti-Aβ biological therapies and optimal dosing so that effective disease modifying therapy now appears imminent. Aβ deposition is a gradual and protracted process, permitting a wide treatment window for anti-Aβ therapies and Aβ PET has made trials in this preclinical AD period feasible. Continuing improvement in Aβ tracer target to background ratio is allowing trials in earlier AD that tailor drug dosage to Aβ level. The quest to standardize quantification and define universally applicable thresholds for all Aβ tracers has produced the Centiloid method. Centiloid values that correlate well with neuropathologic findings and prognosis have been identified. Rapid cloud-based automated individual scan analysis is now possible and does not require MRI. Challenges remain, particularly around cross camera standardized uptake value ratio variation that need to be addressed. This review will compare available Aβ radiotracers, discuss approaches to quantification, as well as the clinical and research applications of Aβ PET.

PET-Amyloid After Inconclusive Cerebrospinal Fluid Biomarkers in Clinical Practice. Is it Necessary to Duplicate Procedures?

INTRODUCTION

In the absence of a gold standard for in vivo Alzheimer disease (AD) diagnosis, AD biomarkers such as cerebrospinal fluid biomarkers (CSF-B) and PET-Amyloid are considered diagnostically useful in clinical practice guidelines and have consensual appropriate use criteria (AUC). However, little evidence has been published on their utilization in the clinical setting or on approaches to mismatched results. The objective of this work was to evaluate the use of AD biomarkers in clinical practice, focusing on the implementation of PET-Amyloid in cases of inconclusive CSF-B.

METHODS

This naturalistic, ambispective case series included patients fulfilling AUC for CSF-B and PET-Amyloid whose CSF-B results were non-diagnostic (target population), analyzing the diagnostic certainty, the treatment approach, and the relationship between CSF-B and PET-Amyloid results.

RESULTS

Out of 2373 eligible patients, AD biomarkers were studied in 417 (17.6%), most frequently due to cognitive impairment in under 65-year-olds, using CSF-B in 311 patients and PET-Amyloid in 150. CSF-B results were non-diagnostic for 44 patients (52.3% male; aged 60.9±6.6 years), who then underwent PET-Amyloid study, which was positive in 31. A 'k' coefficient of 0.108 was obtained between CSF-B and PET-amyloid (54.5% concordance). In multivariate regression analysis, Aβ42 was the only significant predictor (p= 0.018) of a positive PET-Amyloid result. In the target population, PETAmyloid increased diagnostic confidence by 53.7% (p <0.001) and modified the therapeutic approach in 36.4% of cases.

CONCLUSION

These findings support the duplication of AD biomarkers and demonstrate that the implementation of PET-Amyloid provides an early and certain diagnosis to guide appropriate treatment.

Disruption of cholinergic neurotransmission, within a cognitive challenge paradigm, is indicative of Aβ-related cognitive impairment in preclinical Alzheimer's disease after a 27-month delay interval

BACKGROUND

Abnormal beta-amyloid (Aβ) is associated with deleterious changes in central cholinergic tone in the very early stages of Alzheimer's disease (AD), which may be unmasked by a cholinergic antagonist (J Prev Alzheimers Dis 1:1-4, 2017). Previously, we established the scopolamine challenge test (SCT) as a "cognitive stress test" screening measure to identify individuals at risk for AD (Alzheimer's & Dementia 10(2):262-7, 2014) (Neurobiol. Aging 36(10):2709-15, 2015). Here we aim to demonstrate the potential of the SCT as an indicator of cognitive change and neocortical amyloid aggregation after a 27-month follow-up interval.

METHODS

Older adults (N = 63, aged 55-75 years) with self-reported memory difficulties and first-degree family history of AD completed the SCT and PET amyloid imaging at baseline and were then seen for cognitive testing at 9, 18, and 27 months post-baseline. Repeat PET amyloid imaging was completed at the time of the 27-month exam.

RESULTS

Significant differences in both cognitive performance and in Aβ neocortical burden were observed between participants who either failed vs. passed the SCT at baseline, after a 27-month follow-up period.

CONCLUSIONS

Cognitive response to the SCT (Alzheimer's & Dementia 10(2):262-7, 2014) at baseline is related to cognitive change and PET amyloid imaging results, over the course of 27 months, in preclinical AD. The SCT may be a clinically useful screening tool to identify individuals who are more likely to both have positive evidence of amyloidosis on PET imaging and to show measurable cognitive decline over several years.

Predicting clinical decline and conversion to Alzheimer's disease or dementia using novel Elecsys Aβ(1-42), pTau and tTau CSF immunoassays

We evaluated the performance of CSF biomarkers for predicting risk of clinical decline and conversion to dementia in non-demented patients with cognitive symptoms. CSF samples from patients in two multicentre longitudinal studies (ADNI, n = 619; BioFINDER, n = 431) were analysed. Aβ(1-42), tTau and pTau CSF concentrations were measured using Elecsys CSF immunoassays, and tTau/Aβ(1-42) and pTau/Aβ(1-42) ratios calculated. Patients were classified as biomarker (BM)-positive or BM-negative at baseline. Ability of biomarkers to predict risk of clinical decline and conversion to AD/dementia was assessed using pre-established cut-offs for Aβ(1-42) and ratios; tTau and pTau cut-offs were determined. BM-positive patients showed greater clinical decline than BM-negative patients, demonstrated by greater decreases in MMSE scores (all biomarkers: -2.10 to -0.70). Risk of conversion to AD/dementia was higher in BM-positive patients (HR: 1.67 to 11.48). Performance of Tau/Aβ(1-42) ratios was superior to single biomarkers, and consistent even when using cut-offs derived in a different cohort. Optimal pTau and tTau cut-offs were approximately 27 pg/mL and 300 pg/mL in both BioFINDER and ADNI. Elecsys pTau/Aβ(1-42) and tTau/Aβ(1-42) are robust biomarkers for predicting risk of clinical decline and conversion to dementia in non-demented patients, and may support AD diagnosis in clinical practice.

Utility of Amyloid PET Scans in the Evaluation of Patients Presenting with Diverse Cognitive Complaints

BACKGROUND

The impact of amyloid positron emission tomography (Aβ-PET) in a "real-world" memory disorders clinic remains poorly studied.

OBJECTIVE

We studied the impact of Aβ-PET in diagnosis and management in the memory clinic and factors making the most impact in diagnosis and management.

METHODS

We studied 102 patients who had presented at a memory disorders clinic (the Wien Center for Alzheimer's Disease and Memory Disorders, Miami Beach, FL) and had a diagnostic work-up for cognitive complaints, including Aβ-PET scans.

RESULTS

Following Aβ-PET, changes were made in diagnosis (37.3%), in specific treatments for Alzheimer's disease (26.5%) and in psychiatric treatments (25.5%). The agreement between diagnosis pre-Aβ-PET versus post-Aβ-PET diagnosis was only fair, with a Cohen's kappa of 0.23 (95% CI 0-0.42). Patients with MRI findings suggestive of AD (medial temporal and/or parietal atrophy) were more frequently amyloid positive than amyloid negative (66.2% versus 33.8%, p = 0.04). Among patients with atypical clinical features for AD, but with MRI findings suggestive of AD, an amyloid negative PET scan had a greater impact than an amyloid positive PET scan on diagnosis (84.2% versus 17.1%, p < 0.001), management (84.2% versus 40%, p < 0.01) and discussion of results and advice on lifestyle (73.7% versus 22.9%, p < 0.001).

CONCLUSIONS

We conclude that MRI features suggestive of AD predict a positive amyloid PET scan. However, among those with MRI features suggestive of AD but with atypical clinical features of AD, the clinical impact on diagnosis and management is greater for an amyloid negative than an amyloid positive Aβ-PET scans.

A Nomogram for Predicting Amyloid PET Positivity in Amnestic Mild Cognitive Impairment

BACKGROUND

Most clinical trials focus on amyloid-β positive (Aβ+) amnestic mild cognitive impairment (aMCI), but screening failures are high because only a half of patients with aMCI are positive on Aβ PET. Therefore, it becomes necessary for clinicians to predict which patients will have Aβ biomarker.

OBJECTIVE

We aimed to compare clinical factors, neuropsychological (NP) profiles, and apolipoprotein E (APOE) genotype between Aβ+ aMCI and Aβ-aMCI and to develop a clinically useful prediction model of Aβ positivity on PET (PET-Aβ+) in aMCI using a nomogram.

METHODS

We recruited 523 aMCI patients who underwent Aβ PET imaging in a nation-wide multicenter cohort. The results of NP measures were divided into following subgroups: 1) Stage (Early and Late-stage), 2) Modality (Visual, Verbal, and Both), 3) Recognition failure, and 4) Multiplicity (Single and Multiple). A nomogram for PET-Aβ+ in aMCI patients was constructed using a logistic regression model.

RESULTS

PET-Aβ+ had significant associations with NP profiles for several items, including high Clinical Dementia Rating Scale Sum of Boxes score (OR 1.47, p = 0.013) and impaired memory modality (impaired both visual and verbal memories compared with visual only, OR 3.25, p = 0.001). Also, presence of APOEɛ4 (OR 4.14, p < 0.001) was associated with PET-Aβ+. These predictors were applied to develop the nomogram, which showed good prediction performance (C-statistics = 0.79). Its prediction performances were 0.77/0.74 in internal/external validation.

CONCLUSIONS

The nomogram consisting of NP profiles, especially memory domain, and APOEɛ4 genotype may provide a useful predictive model of PET-Aβ+ in patients with aMCI.

Assessment of the appropriate use criteria for amyloid PET in an unselected memory clinic cohort: The ABIDE project

INTRODUCTION

The objective of this study was to assess the usefulness of the appropriate use criteria (AUC) for amyloid imaging in an unselected cohort.

METHODS

We calculated sensitivity and specificity of appropriate use (increased confidence and management change), as defined by Amyloid Imaging Taskforce in the AUC, and other clinical utility outcomes. Furthermore, we compared differences in post-positron emission tomography diagnosis and management change between "AUC-consistent" and "AUC-inconsistent" patients.

RESULTS

Almost half (250/507) of patients were AUC-consistent. In both AUC-consistent and AUC-inconsistent patients, post-positron emission tomography diagnosis (28%-21%) and management (32%-17%) change was substantial. The Amyloid Imaging Taskforce's definition of appropriate use occurred in 55/507 (13%) patients, detected by the AUC with a sensitivity of 93%, and a specificity of 56%. Diagnostic changes occurred independently of AUC status (sensitivity: 57%, specificity: 53%).

DISCUSSION

The current AUC are not sufficiently able to discriminate between patients who will benefit from amyloid positron emission tomography and those who will not.

Association of Amyloid Positron Emission Tomography With Changes in Diagnosis and Patient Treatment in an Unselected Memory Clinic Cohort: The ABIDE Project

Importance

Previous studies have evaluated the diagnostic effect of amyloid positron emission tomography (PET) in selected research cohorts. However, these research populations do not reflect daily practice, thus hampering clinical implementation of amyloid imaging.

Objective

To evaluate the association of amyloid PET with changes in diagnosis, diagnostic confidence, treatment, and patients' experiences in an unselected memory clinic cohort.

Design, Setting, and Participants

Amyloid PET using fluoride-18 florbetaben was offered to 866 patients who visited the tertiary memory clinic at the VU University Medical Center between January 2015 and December 2016 as part of their routine diagnostic dementia workup. Of these patients, 476 (55%) were included, 32 (4%) were excluded, and 358 (41%) did not participate. To enrich this sample, 31 patients with mild cognitive impairment from the University Medical Center Utrecht memory clinic were included. For each patient, neurologists determined a preamyloid and postamyloid PET diagnosis that existed of both a clinical syndrome (dementia, mild cognitive impairment, or subjective cognitive decline) and a suspected etiology (Alzheimer disease [AD] or non-AD), with a confidence level ranging from 0% to 100%. In addition, the neurologist determined patient treatment in terms of ancillary investigations, medication, and care. Each patient received a clinical follow-up 1 year after being scanned.

Main Outcomes and Measures

Primary outcome measures were post-PET changes in diagnosis, diagnostic confidence, and patient treatment.

Results

Of the 507 patients (mean [SD] age, 65 (8) years; 201 women [39%]; mean [SD] Mini-Mental State Examination score, 25 [4]), 164 (32%) had AD dementia, 70 (14%) non-AD dementia, 114 (23%) mild cognitive impairment, and 159 (31%) subjective cognitive decline. Amyloid PET results were positive for 242 patients (48%). The suspected etiology changed for 125 patients (25%) after undergoing amyloid PET, more often due to a negative (82 of 265 [31%]) than a positive (43 of 242 [18%]) PET result (P < .01). Post-PET changes in suspected etiology occurred more frequently in patients older (>65 years) than younger (<65 years) than the typical age at onset of 65 years (74 of 257 [29%] vs 51 of 250 [20%]; P < .05). Mean diagnostic confidence (SD) increased from 80 (13) to 89 (13%) (P < .001). In 123 patients (24%), there was a change in patient treatment post-PET, mostly related to additional investigations and therapy.

Conclusions and Relevance

This prospective diagnostic study provides a bridge between validating amyloid PET in a research setting and implementing this diagnostic tool in daily clinical practice. Both amyloid-positive and amyloid-negative results had substantial associations with changes in diagnosis and treatment, both in patients with and without dementia.

Patient and Caregiver Assessment of the Benefits From the Clinical Use of Amyloid PET Imaging

INTRODUCTION

Few studies to date have explored patient and caregiver views on the clinical use of amyloid positron emission tomography (PET).

METHODS

A 7-item questionnaire assessing patient and caregiver views (510 total respondents) toward amyloid PET imaging was advertised broadly through alz.org/trialmatch.

RESULTS

We received 510 unique responses from 48 US states, 2 Canadian provinces, the Dominican Republic, and Greece. Both patients and caregivers indicated that they would want to receive amyloid imaging if offered the opportunity. Over 88% of respondents had a positive response (∼10% with neutral and 2% with negative responses) to whether amyloid PET should be offered routinely and be reimbursed. Such information was felt to be useful for long-term legal, financial, and health care planning. Respondents identifying with early age cognitive decline (younger than 65 y) were more likely to explore options for disability insurance (P=0.03). Responders from the Midwest were more likely to utilize information from amyloid imaging for legal planning (P=0.02), disability insurance (P=0.02), and life insurance (P=0.04) than other US regions.

DISCUSSION

Patients and caregivers supported the use of amyloid PET imaging in clinical practice and felt that the information would provide significant benefits particularly in terms of future planning.

Impact of amyloid-PET in daily clinical management of patients with cognitive impairment fulfilling appropriate use criteria

To evaluate the use of amyloid-positron emission tomography (PET) in routine clinical practice, in a selected population with cognitive impairment that meets appropriate use criteria (AUC).A multicenter, observational, prospective case-series study of 211patients from 2 level-3 hospitals who fulfilled clinical AUC for amyloid-PET scan in a naturalistic setting. Certainty degree was evaluated using a 5-point Likert scale: 0 (very low probability); 1 (low probability); 2 (intermediate probability); 3 (high probability); and 4 (practically sure), before and after amyloid PET. The treatment plan was considered as cognition-specific or noncognition-specific.Amyloid-PET was positive in 118 patients (55.9%) and negative in 93 patients (44.1%). Diagnostic prescan confidence according amyloid-PET results showed that in both, negative and positive-PET subgroup, the most frequent category was intermediate probability (45.7% and 55.1%, respectively). After the amyloid-PET, the diagnostic confidence showed a very different distribution, that was, in the negative-PET group the most frequent categories are very unlikely (70.7%) and unlikely (29.3%), while in the positive-PET group were very probable (57.6%) and practically sure (39%). Only in 14/211 patients (6.6%) the result of the amyloid-PET did not influence the diagnostic confidence, while in 194 patients (93.4%), the diagnostic confidence improved significantly after amyloid-PET results. The therapeutic intention was modified in 93 patients (44.1%). Specific treatment for Alzheimer disease was started, before amyloid-PET, in 80 patients (37.9%).This naturalistic study provides evidence that the implementation of amyloid-PET is associated with a significant improvement in diagnostic confidence and has a high impact on the therapeutic management of patients with mild cognitive impairment fulfilled clinical AUC.

Impact of Amyloid PET Imaging in the Memory Clinic: A Systematic Review and Meta-Analysis

BACKGROUND

Patients with cognitive impairment or dementias of uncertain etiology are frequently referred to a memory disorders specialty clinic. The impact of and role for amyloid PET imaging (Aβ-PET) may be most appropriate in this clinical setting.

OBJECTIVE

The primary objective of this study was to perform a systematic review and meta-analysis of the impact of Aβ-PET on etiological diagnosis and clinical management in the memory clinic setting.

METHODS

A search of the literature on the impact of Aβ-PET in the memory clinic setting between 1 January 2004 and 12 February 2018 was conducted. Meta-analysis using a random effects model was performed to determine the pooled estimate of the impact of Aβ-PET in the changes of diagnoses and changes in management plan.

RESULTS

After rigorous review, results from 13 studies were extracted, involving 1,489 patients. Meta-analysis revealed a pooled effect of change in diagnoses of 35.2% (95% CI 24.6-47.5). Sub-analyses showed that the pooled effect in change in diagnoses if Aβ-PET was used under the appropriate use criteria (AUC) or non-AUC criteria were 47.8% (95% CI 25.9-70.5) and 29.6% (95% CI: 21.5-39.3), respectively. The pooled effect of a change of diagnosis from Alzheimer's disease (AD) to non-AD and from non-AD to AD were 22.7% (95% CI: 17.1-29.5) and 25.6% (95% CI: 17.6-35.8), respectively. The pooled effect leading to a change of management was 59.6% (95% CI 39.4-77.0).

CONCLUSIONS

Aβ-PET has a highly significant impact on both changes in diagnosis and management among patients being seen at a specialty memory clinic.

Utility of Amyloid and FDG-PET in Clinical Practice: Differences Between Secondary and Tertiary Care Memory Units

The clinical utility of amyloid positron emission tomography (PET) has not been fully established. Our aim was to evaluate the effect of amyloid imaging on clinical decision making in a secondary care unit and compare our results with a previous study in a tertiary center following the same methods. We reviewed retrospectively 151 cognitively impaired patients who underwent amyloid (Pittsburgh compound B [PiB]) PET and were evaluated clinically before and after the scan in a secondary care unit. One hundred and fifty concurrently underwent fluorodeoxyglucose (FDG)-PET. We assessed changes between the pre- and post-PET clinical diagnosis and Alzheimer's disease treatment plan. The association between PiB/FDG results and changes in management was evaluated using χ2 and multivariate logistic regression. Concordance between classification based on scan readings and baseline diagnosis was 66% for PiB and 47% for FDG. The primary diagnosis changed after PET in 17.2% of cases. When examined independently, discordant PiB and discordant FDG were both associated with diagnostic change (p < 0.0001). However, when examined together in a multivariate logistic regression, only discordant PiB remained significant (p = 0.0002). Changes in treatment were associated with concordant PiB (p = 0.009) while FDG had no effect on treatment decisions. Based on our regression model, patients with diagnostic dilemmas, a suspected non-amyloid syndrome, and Clinical Dementia Rating <1 were more likely to benefit from amyloid PET due to a higher likelihood of diagnostic change. We found that changes in diagnosis after PET in our secondary center almost doubled those of our previous analysis of a tertiary unit (9% versus 17.2%). Our results offer some clues about the rational use of amyloid PET in a secondary care memory unit stressing its utility in mild cognitive impairment patients.

A Review of Diagnostic Impact of Amyloid Positron Emission Tomography Imaging in Clinical Practice

BACKGROUND

Molecular imaging of brain amyloid for the diagnosis of Alzheimer's disease (AD) using positron emission tomography (PET) has been approved for use in clinical practice by the Food and Drug Administration (FDA) since 2012. However, the clinical utility and diagnostic impact of amyloid PET imaging remain controversial. We conducted a review of the recent studies investigating clinical utility of amyloid PET imaging with focus on changes in diagnosis, diagnostic confidence, and patient management.

SUMMARY

A total of 16 studies were included in the final analysis. Overall rate of changes in diagnosis after amyloid PET ranged from 9 to 68% (pooled estimate of 31%, 95% CI 23-39%). All studies reported overall increase in diagnostic confidence or diagnostic certainty after amyloid PET. Changes in patient management ranged from 37 to 87%; the most common type of change in management reported was either the initiation or discontinuation of planned AD medications. Key Messages: Amyloid PET imaging led to moderate to significant changes in diagnosis, diagnostic confidence, and subsequent patient management. It may be most useful in patients with high level of diagnostic uncertainty even after the completing the standard workup.

Imaging and Molecular Mechanisms of Alzheimer's Disease: A Review

Alzheimer's disease is the most common form of dementia and is a significant burden for affected patients, carers, and health systems. Great advances have been made in understanding its pathophysiology, to a point that we are moving from a purely clinical diagnosis to a biological one based on the use of biomarkers. Among those, imaging biomarkers are invaluable in Alzheimer's, as they provide an in vivo window to the pathological processes occurring in Alzheimer's brain. While some imaging techniques are still under evaluation in the research setting, some have reached widespread clinical use. In this review, we provide an overview of the most commonly used imaging biomarkers in Alzheimer's disease, from molecular PET imaging to structural MRI, emphasising the concept that multimodal imaging would likely prove to be the optimal tool in the future of Alzheimer's research and clinical practice.

Amyloid imaging for differential diagnosis of dementia: incremental value compared to clinical diagnosis and [18F]FDG PET

Purpose

Cerebral beta-amyloid and regional glucose metabolism assessed by positron emission tomography (PET) are used as diagnostic biomarkers for Alzheimer’s disease (AD). The present study validates the incremental diagnostic value of amyloid PET in addition to clinical diagnosis and [¹⁸F]FDG PET in a real-life memory clinic population.

Methods

Of 138 consecutive patients with cognitive impairment who received combined [¹⁸F]FDG and [¹¹C]PIB PET, 84 were diagnosed with major neurocognitive disorder (DSM-5) and included. Baseline clinical and [¹⁸F]FDG PET diagnoses were independently established with and without access to amyloid PET results and were dichotomized into AD or non-AD disorders. The incremental value of amyloid PET was evaluated in terms of: (1) the change in clinical and [¹⁸F]FDG PET diagnoses, (2) the change in agreement between clinical and [¹⁸F]FDG PET diagnoses, and (3) diagnostic accuracy using an interdisciplinary consensus diagnosis after an extended follow-up (2.4 ± 1.3 years after PET) as the reference.

Results

After disclosure of the amyloid PET results, clinical and [¹⁸F]FDG PET diagnoses changed in 23% and 18% of patients, respectively, and agreement between both ratings increased from 62% to 86% (p < 0.001). The accuracy of clinical and [¹⁸F]FDG PET diagnoses improved from 71% to 89% (p < 0.01) and from 76% to 94% (p < 0.001), respectively. The additional value of amyloid PET was rather uniform in relation to age at onset and consistency with appropriate use criteria.

Conclusion

Amyloid PET provides significant incremental diagnostic value beyond clinical and [¹⁸F]FDG PET diagnoses of AD. Given the high diagnostic accuracy of combined clinical and amyloid PET assessment, further studies are needed to clarify the role of an additional [¹⁸F]FDG PET scan in these patients.

Emerging topics and practical aspects for an appropriate use of amyloid PET in the current Italian context

In May 2017 some representatives of the Italian nuclear medicine and neurological communities spontaneously met to discuss the issues emerged during the first two years of routine application of amyloid PET with fluorinated radiopharmaceuticals in the real world. The limitations of a binary classification of scans, the possibility to obtain early images as a surrogate marker of regional cerebral bloos flow, the need for (semi-)quantification and, thus, the opportunity of ranking brain amyloidosis, the correlation with Aβ42 levels in the cerebrospinal fluid, the occurrence and biological meaning of uncertain/boderline scans, the issue of incidental amyloidosis, the technical pittfalls leading to false negative/positive results, the position of the tool in the diagnostic flow-chart in the national reality, are the main topics that have been discussed. Also, a card to justify the examination to be filled by the dementia specialist and a card for the nuclear medicine physician to report the exam in detail have been approved and are available in the web, which should facilitate the creation of a national register, as previewed by the 2015 intersocietal recommendation on the use of amyloid PET in Italy. The content of this discussion could stimulate both public institutions and companies to support further research on these topics.

Quantitative appraisal of the Amyloid Imaging Taskforce appropriate use criteria for amyloid-PET

INTRODUCTION

We test the hypothesis that amyloid-positron emission tomography prescriptions, considered appropriate based on the Amyloid Imaging Taskforce (AIT) criteria, lead to greater clinical utility than AIT-inappropriate prescriptions.

METHODS

We compared the clinical utility between patients who underwent amyloid-positron emission tomography appropriately or inappropriately and among the subgroups of patients defined by the AIT criteria. Finally, we performed logistic regressions to identify variables associated with clinical utility.

RESULTS

We identified 171 AIT-appropriate and 67 AIT-inappropriate patients. AIT-appropriate and AIT-inappropriate cases did not differ in any outcomes of clinical utility (P > .05). Subgroup analysis denoted both expected and unexpected results. The logistic regressions outlined the primary role of clinical picture and clinical or neuropsychological profile in identifying patients benefitting from amyloid-positron emission tomography.

DISCUSSION

Contrary to our hypothesis, also AIT-inappropriate prescriptions were associated with clinical utility. Clinical or neuropsychological variables, not taken into account by the AIT criteria, may help further refine criteria for appropriateness.

Lacrimal gland uptake on F-18 florbetapir amyloid positron emission tomography scan

In 2012, the Food and Drug Administration (FDA) approved the use of F-18 florbetapir to estimate β-amyloid neuritic plaque density when indicated. A normal scan will show increased radiotracer uptake in the white matter. Mild uptake in salivary glands, skin, muscles, and bones is considered normal. Being a new and infrequently performed study, familiarity with normal biodistribution and variants is important. We hereby present 2 cases with F-18 florbetapir uptake in lacrimal glands. Patients had no symptoms or known systemic conditions to explain this uptake. We speculate that lacrimal gland uptake of F-18 florbetapir could represent a normal variant.

Clinical Use and Utility of Amyloid Imaging

Currently, 3 amyloid PET tracers are approved and commercially available for clinical use. They allow for the accurate in vivo detection of amyloid plaques, one hallmark of Alzheimer disease. Here, we review the current knowledge on the clinical use and utility of amyloid imaging. Appropriate use criteria for the clinical application of amyloid imaging are established, and most currently available data point to their validity. Visual amyloid image analysis is highly standardized. Disclosure of amyloid imaging results is desired by many cognitively impaired subjects and seems to be safe once appropriate education is delivered to the disclosing clinicians. Regarding clinical utility, increasing evidence points to a change in diagnosis via amyloid imaging in about 30% of cases, to an increase in diagnostic confidence in about 60% of cases, to a change in patient management in about 60% of cases, and specifically to a change in medication in about 40% of cases. Also, amyloid imaging results seem to have a relevant impact on caregivers. Further, initial simulation studies point to a potential positive effect on patient outcome and to cost effectiveness of amyloid imaging. These features, however, will require confirmation in prospective clinical trials. More work is also required to determine the clinical utility of amyloid imaging specifically in subjects with mild cognitive impairment and in comparison with or in conjunction with other Alzheimer disease biomarkers. In summary, the clinical use of amyloid imaging is being studied, and the currently available data point to a relevant clinical utility of this imaging technique. Ongoing research will determine whether this accurate and noninvasive approach to amyloid plaque load detection will translate into a benefit to cognitively impaired subjects.

Communicating mild cognitive impairment diagnoses with and without amyloid imaging

Background

Mild cognitive impairment (MCI) has an uncertain etiology and prognosis and may be challenging for clinicians to discuss with patients and families. Amyloid imaging may aid specialists in determining MCI etiology and prognosis, but creates novel challenges related to disease labeling.

Methods

We convened a workgroup to formulate recommendations for clinicians providing care to MCI patients.

Results

Clinicians should use the MCI diagnosis to validate patient and family concerns and educate them that the patient’s cognitive impairment is not normal for his or her age and education level. The MCI diagnosis should not be used to avoid delivering a diagnosis of dementia. For patients who meet Appropriate Use Criteria after standard-of-care clinical workup, amyloid imaging may position specialists to offer more information about etiology and prognosis. Clinicians must set appropriate expectations, including ensuring that patients and families understand the limitations of amyloid imaging. Communication of negative results should include that patients remain at elevated risk for dementia and that negative scans do not indicate a specific diagnosis or signify brain health. Positive amyloid imaging results should elicit further monitoring and conversations about appropriate advance planning. Clinicians should offer written summaries, including referral to appropriate social services.

Conclusions

In patients with MCI, there is a need to devote considerable time and attention to patient education and shared decision-making. Amyloid imaging may be a tool to aid clinicians. Careful management of patient expectations and communication of scan results will be critical to the appropriate use of amyloid imaging information.