'Medical University Prof. Dr. Paraskev Stoyanov - Varna'
Doi
Abstract
We tested 181 dried urine samples spotted on regular cosmetic cotton swabs for quantitative analysis of various potentially alcoholic beverage related metabolites across wide polarity and structural ranges. The samples were collected in a 3-week cross-over intervention trial with alcoholic beverages and abstention. The agreement of measurements between conventional 24-hour urines and dried urine spots made from them in situ corrected with creatinine ratio was evaluated by Passing-Bablok regression and Bland-Altman analysis. Determinations were performed by a recently developed and fully validated UPLC-MSMS multiplex method. There was full agreement in qualitative results making dried urine spots suitable for metabolomics profiling and screening analysis useful for compliance control in clinical trials. Quantitative analysis exposed certain limitations of dried spotting. Based on the slopes calculated from Passing-Bablok regression, results were underestimated in the range of 11-23% in case of tartaric acid, indoxyl sulfate, pyroglutamyl proline and dihydroepiandrosterone sulphate. Agreement was found in case of the alcohol intake related metabolites, ethyl sulfate and ethyl glucuronide. Partial overestimation ranging from 10-20% was observed for cresol sulfate. As a secondary objective, we examined variance of individual total daily creatinine excretion which was found to be up to 16%, comparing seven 24-hour urine samples collected from each of the 26 subjects. This finding suggests that a creatinine correction factor could be calculated as an average individual value obtained from several 24 hour urine samples. A creatinine correction factor could be useful in some long-term clinical trials for correction of measurements in dried urine spots provided that the resulting analytical error is acceptable for the research purpose
