Cerebrospinal Fluid Aß42/Aß40 as a Means to Limiting Tube- and Storage-Dependent Pre-Analytical Variability in Clinical Setting.

BACKGROUND: Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers have recently been included in the criteria for AD diagnosis. Unfortunately, their wider use in routine and interpretation require more standardization, particularly for the pre-analytical steps. In particular, amyloid-ß (Aß)42 peptide measurement is strongly influenced by the type of collection tube and by repeated freeze/thaw cycles. OBJECTIVE: The objectives of this study were to compare, in clinical setting, the impact of collection tubes and the repetition of freeze/thaw cycles on Aß42 and Aß40 concentrations and consequently determine if the Aß42/Aß40 ratio could resolve the diagnosis difficulties related to these pre-analytical parameters. METHODS: CSF from 35 patients was collected in different polypropylene (PP) and stored at - 80°C after sampling. For CSF collected in the reference tube, three successive freeze-thaw cycles were done. Aß42 and Aß40 concentrations were determined in each condition in order to calculate the Aß42/Aß40 ratio. RESULTS: Our results showed that CSF Aß42 and Aß40 values were significantly different according to the type of collection tube and the number of freeze/thaw cycles. Although the calculation of the Aß42/Aß40 ratio eliminated the effect of PP tube-dependent variation, this was not the case for freeze-thaw cycle-associated variation. CONCLUSION: The use of Aß42/Aß40 ratio rather than Aß42 alone could contribute toward pre-analytical standardization, thus allowing the general use of CSF AD biomarkers in routine practice.

Gastric Wall Fatty Infiltration in Patients Without Overt Gastrointestinal Disease.

OBJECTIVE: The purpose of this study was to evaluate the frequency of gastric wall fatty infiltration in patients without overt gastrointestinal disease. MATERIALS AND METHODS: A retrospective study included patients who underwent unenhanced MDCT for renal colic. Two radiologists reviewed all of the images and evaluated for the presence of gastric wall fatty infiltration. The following patient characteristics were also recorded: sex, age, body mass index, total and visceral fat area, and presence of colic or ileal fat halo sign, or hepatic steatosis. A t test and Fisher test were used to compare the results between patients with and patients without gastric wall fatty infiltration. RESULTS: Gastric wall fatty infiltration was present in 25 of 120 (21%) patients in the study. Mean age, weight, body mass index, visceral and total fat areas, proportion of hepatic steatosis, number of men, and frequency of the presence of colic and ileal fat halo signs were significantly higher among patients with gastric wall fatty infiltration than in those without infiltration. CONCLUSION: Gastric wall fatty infiltration was significantly more frequent in men older than 45 years and patients with a body mass index greater than 25. It may represent a normal finding, but its relation to other pathologic conditions related to obesity remains to be explored.