Background: Brain glucose hypometabolism is an invariant feature and has significant diagnostic value for Alzheimer's disease. Thiamine diphosphate (TDP) is a critical coenzyme for glucose metabolism and significantly reduced in brain and blood samples of patients with Alzheimer's disease (AD).
Aims: To explore the diagnostic value of the measurement of blood thiamine metabolites for AD.
Methods: Blood TDP, thiamine monophosphate, and thiamine levels were detected using high performance liquid chromatography (HPLC). The study included the exploration and validation phases. In the exploration phase, the samples of 338 control subjects and 43 AD patients were utilized to establish the models for AD diagnosis assayed by receiver operating characteristic (ROC) curve, including the variable γ that represents the best combination of thiamine metabolites and age to predict the possibility of AD. In the validation phase, the values of models were further tested for AD diagnosis using samples of 861 control subjects, 81 AD patients, 70 vascular dementia patients, and 13 frontotemporal dementia patients.
Results: TDP and the γ exhibited significant and consistent values for AD diagnosis in both exploration and validation phases. TDP had 0.843 and 0.837 of the areas under ROC curve (AUCs), 77.4% and 81.5% of sensitivities, and 78.1% and 77.2% of specificities respectively in the exploration and validation phases. The γ had 0.938 and 0.910 of AUCs, 81.4% and 80.2% of sensitivities, and 90.5% and 87.2% of specificities respectively in the exploration and validation phases. TDP and the γ can effectively distinguish AD from vascular dementia (64.3% for TDP, 67.1% for γ) and frontotemporal dementia (84.6% for TDP, 100.0% for γ). Interpretation. The measurement of blood thiamine metabolites by HPLC is an ideal diagnostic test for AD with inexpensive, easy to perform, noninvasive merits.
Keywords: Alzheimer's disease; Biomarker; Blood; Diagnosis; Thiamine metabolites.