ABSTRACT
INTRODUCTION: The analysis of the core biomarkers of Alzheimer's Disease (AD) in the cerebrospinal fluid (CSF) is recommended in the clinical units where it is available. Because of the absence of universal validated values, the determination of specific cut-off points for each center and its population is recommended. The main objective of the CORCOBIA study was to determine the cut-off points of core AD CSF biomarkers for several centers (Parc de Salut Mar, Barcelona and Hospital General de Granollers), which work with the same reference laboratory (Laboratori de Referència de Catalunya). METHODS: Prospective study including cognitively unimpaired individuals (CU, n = 42), subjects with amnestic mild cognitive impairment (aMCI, n = 35) and patients with dementia due to Alzheimer's Disease (AD, n = 48), in whom clinical and neuropsychological assessment, neuroimaging, APOE genotyping and lumbar puncture to analyse amyloid beta peptides (Aß42, Aß40), total tau (tTau) and phosphorylated Tau (pTau181) using the Lumipulse G600II (Fujirebio) was performed. The values of sensitivity (SE), specificity (SP), predictive values and area under the curve (AUC) were calculated, determining the cut-off point according to the Youden index by comparing the CU and AD groups. RESULTS: The resulting cut-offs and their AUC were the following: Aß42 750 pg/mL (AUC 0.809); Aß42/Aß40 0.062 (AUC 0.78); pTau181 69.85 pg/mL (AUC 0.81); tTau 522.0 pg/mL (AUC 0.79); Aß42/tTau 1.76 (AUC 0.86); Aß42/pTau181 10.25 (AUC 0.86). CONCLUSIONS: The determination of cut-off points of core AD CSF biomarkers for the participating centers allows a better diagnostic accuracy. The ratio CSF Aß42/pTau181 shows the highest AUC and better balance between sensitivity and specificity.
ABSTRACT
OBJECTIVE: The variability of both phenotypic and genotypic expression in mitochondrial diseases makes clinical diagnosis difficult, which is essential to establish therapy, aid in genetic counselling or for performing prenatal diagnosis. We have therefore proposed a strategy to help determine correct diagnosis of these alterations, in an attempt to rationalize the number of tests and, whenever possible, avoid tissue biopsy and minimize the size of the biopsy when indicated. DEVELOPMENT: Based on mitochondrial metabolism and molecular bases, as well as their alterations, a preliminary metabolic examination is carried out including at least one study of cytoplasmatic (lactate/pyruvate) and mitochondrial oxide reduction (hydroxibutirate/acetoacetate) in basal conditions or, if required, following glucose overload or an effort test. Metabolic study, in addition to clinical exploration, are the screening tests used to determine the need for tissue biopsy in which biochemical (pyruvate dehydrogenase, free and total carnitine, beta oxidation enzymes and respiratory chain complexes), genetic (mitochondrial DNA or nuclear alterations) and histologic tests are carried out to confirm diagnosis. CONCLUSIONS: a) Metabolic exploration may discard mitochondrial disease and many cases, avoid the use of an invasive procedure such as tissue biopsy. b) Biochemical study of tissue biopsy is the only useful key in the confirming of the diagnosis when no mitochondrial and/or nuclear DNA are observed.
