en Clinical Biochemistry Clinical Biochemistry Original Research: Clinical Science Original Research: Clinical Science <strong>Background: </strong>The pathogenesis of Alzheimer&rsquo;s disease (AD) is believed to be occurred by the production of neurotic plaques of the beta-amyloid peptide (A&beta;) and deposition of them. Therefore, biomarkers of abnormal A&beta; processing may represent before the AD clinical biomarkers, which could be benefit for a successful disease management that may prevent the AD development. The aim of this study is to investigate of plasma A&beta;40,42 levels in Alzheimer&#39;s patients in Syria and thus determine whether they may have a potential role as biomarker for identifying and predicting AD.<br> &nbsp;&nbsp; <strong>Methods:</strong> In this cross-sectional study, the plasma levels of A&beta;1-40 and A&beta;1-42 were investigated in two groups represent Syrian population, AD group; clinically diagnosed AD patients (n=50) and CN group; cognitively normal participants (n=33). This study first determined the reference interval of plasma A&beta;1-40 and A&beta;1-42 for cognitively normal Syrian. Results were analyzed using SPSS, 24, depending on independent-samples t test, considering that the value of p < 0.05 is statistically significant.<br> &nbsp;&nbsp; <strong>Results:</strong> The results showed that the plasma levels of A&beta;1-40 (p<0.001, OR=1.031, 95%CI: 1.012-1.051) and A&beta;1-42 (p<0.001, OR=1.306, 95%CI: 1.145-1.490) were significantly higher in AD patients than in cognitively normal participants, and no significant association was shown between both of education and sex with plasma A&beta; levels.<br> &nbsp;&nbsp; <strong>Conclusion:</strong> The plasma levels of A&beta;1-40 and A&beta;1-42 could be potential biomarkers for identifying and predicting AD. Alzheimer disease, Aβ40,42, Biomarkers, Syria 127 131 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-6049-1&slc_lang=en&sid=1 Rafah Manafikhi rafahmanafikhi@gmail.com 200319475328460063472 200319475328460063472 Yes Department of Biochemistry and Microbiology, Faculty of Pharmacy, University of Damascus, Syria M. Bassam Haik dr_b_haik@hotmail.com 200319475328460063473 200319475328460063473 No General Manager of the General Committee of Ibn Khaldun Hospital, Aleppo, Syria Raghda Lahdo raghdals@yahoo.fr 200319475328460063474 200319475328460063474 No Department of Biochemistry and Microbiology, Faculty of Pharmacy, University of Aleppo, Syria Faizeh AlQuoubaili faizehalquobaili@gmail.com 200319475328460063475 200319475328460063475 No Department of Biochemistry and Microbiology, Faculty of Pharmacy, University of Damascus, Syria