Background: Alzheimer's disease (AD) biomarkers are of great relevance in clinical research, especially after the AT(N) framework. They enable early diagnosis, disease staging and research with new promising drugs, monitoring therapeutic response. However, the high cost and low availability of the most well-known methods limits their use in low and medium-income countries. In this context, Millipore xMap® Luminex may be a cost-effective alternative. In our study, using INNOTEST® as reference, we assess the diagnostic accuracy of Millipore xMap® and propose a cutoff point for AD.Methods: We performed lumbar puncture of seven older individuals with clinically defined AD, 17 with amnestic mild cognitive impairment (aMCI) and 11 without objective cognitive impairment-control group (CG). Cerebrospinal fluid (CSF) biomarkers concentrations for aB42, p-Tau, and t-Tau were measured by INNOTEST® and Millipore xMap®, and then the techniques were compared to assess the diagnostic accuracy of the new test and to define a cutoff.Results: INNOTEST® and Millipore xMap® measurements showed all correlations >0.8 for the same biomarker, except for t-Tau that was 0.66. Millipore xMap® measurements showed a robust accuracy for all biomarkers, with AUC higher than 0.808 (t-Tau), and the best for Aβ42 (AUC = 0.952). The most accurate cutoffs were found at 1012.98 pg/ml (Aβ42), 64.54 pg/ml (p-tau), 3251.81 pg/ml (t-tau), 3.370 (t-Tau/Aβ42), and 0.059 (p-Tau/Aβ42).Conclusion: Given its good accuracy and cost-effectiveness, Milliplex xMap® tests seems a reliable and promising tool, especially for low and middle-income countries.
Background Comparison between functionality and cognition in elderly patients with Alzheimer’s dementia (AD) and without cognitive impairment with positive and negative Aβ‐42 and p‐Tau biomarkers evaluated using the Luminex technique. Method Patients with Alzheimer’s dementia and normal cognition (control) were recruited. They were divided in two groups according to their clinical diagnosis: AD group (n=30) and control group (CTRL) (n=10). The AD group was then divided in patients with positive (n=21) and negative (n=9) Aβ‐42 and p‐Tau biomarkers. The participants were submitted to sociodemographic. The general cognition was evaluated through the following instruments: the Mini‐Mental State Examination (MMSE), semantic verbal fluency (SVF), animal fluency, short term memory, and recognition of CERAD battery, and functionality was evaluated by the Pfeffer scale. Samples from the cerebrospinal fluid (CSF) of patients were collected, processed, and stored at ‐80°C until use. The Luminex technique was then used for the Aβ‐42, t‐Tau, p‐Tau, t‐Tau/Aβ‐42 ratio, and p‐Tau/Aβ‐42 ratio biomarker analysis. Obtained data was processed and analyzed through the software SPSS 22.0. Result Comparison between control patients and patients with AD, as defined by clinical diagnosis, did not show significant differences regarding to Aβ‐42 expression in CSF (U=91,000; p=0,067), (AD=1119,0360, SD=708,98952 vs CTRL=775,2623 SD=341,67835). However, there was a significant difference between groups concerning t‐Tau protein, (U=198,500; p=0,028), p‐Tau (U=250,00, p=0,001) and p‐Tau/Aβ‐42 ratio (U=238,00; p=0,005). In terms of cognitive variables, all showed significant differences between groups: MMSE (U=46,500, p=0,001), SVF (U=39,000; p<0,001), short term memory (U=27,000, p<0,001), recognition (U=72,500,p=0,014), as well as functionality (U=258,500, p<0,001). There was no difference regarding the age (U= 201,500; p=0,109) and formal education (U=201,500, p=0,109). As for the AD groups with positive and negative biomarkers, there was no significant difference in cognitive variables, age, formal education, and functionality. Conclusion AD group with negative biomarkers non differ in terms of cognition. Comparing the control and AD groups, there were differences in functionality, cognition, and biomarkers. However, comparing AD groups in terms of biomarkers, there was no difference in functionality performance, short‐term memory, fluency and general cognition. Therefore, the biomarkers do not indicate significant cognitive differences in the group of patients with dementia.
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