Demographics and clinical characteristics
A total of 96 subjects were included in the study. The average age of total subjects was 71.50 ± 9.73 years old, and 42 subjects (43.8%) were male. Among total cohort 68 (70.8%) subjects presented amyloid-positive and 28 subjects were amyloid-negative. Comparison of baseline characteristics between groups is demonstrated in Table 1. There was no significant difference in age, sex, education level, and frequency of APOE ε4 carrier between groups. Amyloid-positive groups showed poor MMSE scores reflecting poor general cognitive function, and higher CDR and CDR-SOB indicating increased disease severity. Correspondingly, amyloid-positive group contained more AD patients than amyloid-negative group. Amyloid-positive group presented significantly higher MDS-OAβ value with plasma oligomeric Aβ concentration of 0.88 ng/ml than amyloid-negative group with 0.68 ng/ml (Figure 1).
Table 1. Demographics and clinical characteristics of subjects
|
Amyloid-negative
(N=28)
|
Amyloid-positive
(N=68)
|
p value
|
Age, years
|
74.00 (70.50–79.00)
|
70.00 (61.00–75.50)
|
0.058
|
Male, n (%)
|
13 (46.43)
|
29 (42.65)
|
0.910
|
Education, years
|
16.00 (12.00–16.00)
|
16.00 (12.00–16.00)
|
0.783
|
APOEε4 carrier, n (%)
|
9 (36.0)
|
32 (55.17)
|
0.173
|
Diagnosis
|
|
|
<0.001
|
AD/MCI/SCD/OND*, n
|
4/11/6/7
|
50/16/1/1
|
|
MMSE
|
24.00 (20.00–26.00)
|
19.00 (11.00–25.00)
|
0.016
|
CDR
|
0.5 (0.5–0.75)
|
1.0 (0.5–1.0)
|
0.003
|
CDR-SOB
|
3.0 (2.0–4.25)
|
6.0 (2.0–8.0)
|
0.014
|
MDS-OAβ, ng/ml
|
0.68 (0.52–0.77)
|
0.88 (0.80–0.97)
|
<0.001
|
Data are presented as the median (interquartile range) unless otherwise specified.
* OND includes FTD, PSP, PDD, and CBS.
AD; Alzheimer’s Disease, CBS; Corticobasal Syndrome, CDR; Clinical Dementia Rating, CDR-SOB; Clinical Dementia Rating Sum of Boxes, FTD; Frontotemporal Dementia, MCI; Mild Cognitive Impairment, MMSE; Mini-Mental-State-Examination, MDS-OAβ; Multimer Detection System-Oligomeric Amyloid-β, OND; Other Neurodegenerative Disease, PDD; Parkinson’s Disease Dementia, PSP; Progressive Supranuclear Palsy, SCD; Subjective Cognitive Decline.
Figure 1. Concentration of plasma MDS-OAβ according to groups
AD; Alzheimer’s Disease, MCI; Mild Cognitive Impairment, MDS-OAβ; Multimer Detection System-Oligomeric Amyloid-β, OND; Other Neurodegenerative Disease, SCD; Subjective Cognitive Decline.
MDS-OAβ as a predictor of amyloid status
MDS-OAβ positivity could differentiate amyloid-positive subjects from amyloid-negative subjects with sensitivity of 85.3% and specificity of 85.7% (AUC= 0.855, 95% CI = 0.776–0.933). Multivariate models with MDS-OAβ positivity and other covariates including age, MMSE score, and APOE ε4 status showed much better performance with AUC values between 0.892 and 0.926 than multivariate models without MDS-OAβ positivity (Table 2). Among various combinations of predictors, MDS-OAβ positivity combined with age, APOE ε4 status, and MMSE score demonstrated the highest AUC value of 0.926 (0.871–0.980).
MDS-OAβ positivity alone presented better predictability than MMSE alone (AUC= 0.657, 95% CI = 0.545–0.769). Although, when combined with age and APOE ε4 status, the AUC value for MMSE increased to 0.740 (95% CI = 0.626–0.853), this was not statistically significant compared with MMSE alone. However, when the combination of predictors were added with MDS-OAβ positivity, predictive performance improved significantly (AUC= 0.926, 95% CI = 0.871–0.980) (Figure 2. A). When combining objective factors such as age and APOE ε4 status with MDS-OAβ positivity, the predictability on amyloid PET positivity was strengthened (Figure 2. B).
Table 2. Performance of predictors for amyloid PET positivity with and without MDS-OAβ positivity
Predictors
|
AUC (95% CI)
|
Sensitivity (%)
|
Specificity (%)
|
MMSE
|
0.657
(0.545–0.769)
|
54.4
|
82.1
|
age + MMSE
|
0.681
(0.572–0.789)
|
47.1
|
89.3
|
age + APOEε4
|
0.684
(0.552–0.816)
|
77.6
|
60.0
|
age + APOEε4 + MMSE
|
0.740
(0.626–0.853)
|
56.9
|
84.0
|
MDS-OAβ positivity
|
0.855
(0.776–0.933)
|
85.3
|
85.7
|
MMSE +
MDS-OAβ positivity
|
0.892
(0.820–0.963)
|
86.8
|
85.7
|
age + MMSE +
MDS-OAβ positivity
|
0.922
(0.863–0.981)
|
91.2
|
82.1
|
age + APOE ε4 +
MDS-OAβ positivity
|
0.912
(0.844–0.980)
|
74.1
|
96.0
|
age + APOE ε4 + MMSE +
MDS-OAβ positivity
|
0.926
(0.871–0.980)
|
74.1
|
96.0
|
AUC; area under the curve, CI; confidential interval, MMSE; Mini-Mental-State-Examination, MDS-OAβ; Multimer Detection System-Oligomeric Amyloid-β
Figure 2. Receiver Operating Characteristic analysis of MDS-OAβ positivity with other predictors on amyloid PET positivity
- Added MDS-OAβ positivity to clinical information such as age, MMSE score, and APOE ε4 status, predictability for amyloid PET positivity improves. B. Considered only objective factors such as age and APOE ε4 status, combining with MDS-OAβ positivity strengthened the predictability on amyloid PET positivity
MDS-OAβ; Multimer Detection System-Oligomeric Amyloid-β, MMSE; Mini-Mental-State-Examination.