Serum Amyloid Beta Peptides in Patients with Dementia and Age-Matched Non-Demented Controls as Detected by Surface-Enhanced Laser Desorption Ionisation-Time of Flight Mass Spectrometry (SELDI-TOF MS)

Background: By using surface enhanced laser desorption/ionisation-time of flight mass spectrometry (SELDI-TOF MS) an amyloid ss (Ass) profile was shown in cerebrospinal fluid (CSF) of patients with dementia. Objective: To investigate the A beta-profile in serum with SELDI-TOF MS, to evaluate if this profile resembles CSF profiles and to investigate the correlation between intensity of A beta-peptide-peaks in serum and clinical, demographical and genetic variables. Methods: Duplicate profiling of Ass by an SELDI-TOF MS immunocapture assay was performed in 106 patients, suffering from Alzheimer's Disease or Vascular Dementia and age-matched non-demented control patients. Linear regression analyses were performed to investigate the intensities of four selected A beta peaks as dependent variables in relation to the independent clinical, demographic or genetic variables. Results: Ass37, Ass38 and Ass40 were found among additional unidentified Ass peptides, with the most pronounced Ass peak at a molecular mass of 7752. This profile partly resembled the CSF profile. The clinical diagnosis was not a predictive independent variable, however ABCB1 genotypes C1236T, G2677T/A, age and creatinine level showed to be related to Ass peak intensities in multivariate analyses. Conclusions: We found an Ass profile in serum that partly resembled the CSF profile in demented patients. Age, creatinine levels, presence of the APOE epsilon 4 allele and ABCB1 genotypes (C1236T and G2677T/A) were correlated with the A beta serum profile. The role of P-gp as an Ass transporter and the role of ABCB1 genotypes deserves further research. The investigated serum A beta profile is probably not useful in the diagnosis of dementia.