The influence of diagnosis, intra- and inter-person variability on serum and plasma Abeta levels.
Evidence suggests that high peripheral beta-amyloid (Abeta)(1-40) levels and low ratios of Abeta(1-42)/Abeta(1-40) are associated with increased risk for Alzheimer's disease (AD). In this cross-sectional design, serum and plasma samples from 67 AD patients and 146 controls (similar in age and gender) were evaluated using Abeta(1-40) and Abeta(1-42) ELISA. Coefficient of variance was calculated for intra- and inter-person variability of Abeta(1-40) and Abeta(1-42). Abeta(1-40) correlated with age, MMSE and their Abeta(1-42)/Abeta(1-40) ratios (p<0.05). Significantly higher Abeta(1-40) levels were observed in AD patients than controls (p<0.05) but no difference was observed for Abeta(1-42) (p>0.05). Serum Abeta(1-42)/Abeta(1-40) ratios were also significantly lower in AD patients than controls (p<0.05). Lower intra-person than inter-person variability was observed for serum and plasma Abeta(1-40) and Abeta(1-42) and these were higher in controls than in AD patients. The intra-person variability of serum Abeta(1-40) did not influence the group differences observed between AD patients and controls. Significant interaction was observed between diagnosis and intra-person variability for serum Abeta(1-40) levels (p<0.05) and was supported by our finding of higher intra-person variability for serum Abeta(1-40) in controls (26.97%) than in AD patients (18.35%). We confirm the previously observed differences in blood Abeta levels between AD and control groups. In addition, we now report the presence of high intra- and inter-person variability possibly due to factors that influence peripheral Abeta levels and warrant further investigation before the potential use of Abeta as an AD biomarker can be fully exploited.
Abdullah
Laila
L
Roskamp Institute, 2040 Whitfield Avenue, Sarasota, FL 34243, United States. labdullah@rfdn.org
Paris
Daniel
D
Luis
Cheryl
C
Quadros
Amita
A
Parrish
Julia
J
Valdes
Luis
L
Keegan
Andrew P
AP
Mathura
Venkatarajan
V
Crawford
Fiona
F
Mullan
Michael
M
D000368:Aged; D000544:Alzheimer Disease / Q000097:blood* / Q000175:diagnosis* / Q000503:physiopathology; D016229:Amyloid beta-Peptides / Q000032:analysis / Q000097:blood*; D015415:Biomarkers / Q000032:analysis / Q000097:blood; D001798:Blood Proteins / Q000032:analysis; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D014644:Genetic Variation / Q000502:physiology; D006801:Humans; D008297:Male; D010446:Peptide Fragments / Q000032:analysis / Q000097:blood*; D010949:Plasma / Q000378:metabolism; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity
D016229:Amyloid beta-Peptides; D015415:Biomarkers; D001798:Blood Proteins; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)