title: Validity of extracellular water assessment with saliva samples using plasma as the reference biological fluid.
abstract: Extracellular water (ECW) assessment is based on dilution techniques, commonly using blood sampling. However, plasma collection is an invasive procedure. We aimed to validate the use of saliva for ECW estimation by the bromide dilution technique using plasma as the reference method, in a sample of elite athletes. A total of 89 elite athletes with a mean age of 20.4 ± 4.4 years were evaluated. Baseline samples were collected before sodium bromide oral dose administration, and enriched samples were collected 3 h post-dose administration. The bromide concentration was assessed by high-performance liquid chromatography. Comparison of means, concordance coefficient correlation (CCC), multiple regression and Bland-Altman analysis were performed. The ECW from saliva explained 91% of the variance in ECW by plasma with a standard error of estimation of 0.91 kg. The CCC between alternative and reference methods was 0.952. No significant trend was observed between the mean and difference of the methods, with limits of agreement ranging between -1.5 and 2.1 kg. These findings reveal that bromide dilution volume calculated from saliva samples is a valid noninvasive method for ECW assessment in elite athletes.
authors.affiliation: Exercise and Health Laboratory, Faculty of Human Kinetics-Technical University of Lisbon, Estrada da Costa,, 1499-688, Cruz-Quebrada, Portugal.
authors.forename: Catarina N
authors.initials: CN
authors.lastname: Matias
authors.forename: Analiza M
authors.initials: AM
authors.lastname: Silva
authors.forename: Diana A
authors.initials: DA
authors.lastname: Santos
authors.forename: Luis A
authors.initials: LA
authors.lastname: Gobbo
authors.forename: Dale A
authors.initials: DA
authors.lastname: Schoeller
authors.forename: Luís B
authors.initials: LB
authors.lastname: Sardinha
mesh_terms: D000293:Adolescent; D056352:Athletes; D001834:Body Water / Q000737:chemistry*; D001965:Bromides / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005110:Extracellular Space / Q000737:chemistry; D005260:Female; D006801:Humans; D008297:Male; D010949:Plasma / Q000737:chemistry*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry*; D017670:Sodium Compounds / Q000737:chemistry; D014867:Water / Q000032:analysis*; D055815:Young Adult
chemical_list: D001965:Bromides; D017670:Sodium Compounds; D014867:Water; C027938:sodium bromide