title: Variability in baseline laboratory measurements of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).
abstract: Multi-center epidemiological studies must ascertain that their measurements are accurate and reliable. For laboratory measurements, reliability can be assessed through investigation of reproducibility of measurements in the same individual. In this paper, we present results from the quality control analysis of the baseline laboratory measurements from the ELSA-Brasil study. The study enrolled 15,105 civil servants at 6 research centers in 3 regions of Brazil between 2008-2010, with multiple biochemical analytes being measured at a central laboratory. Quality control was ascertained through standard laboratory evaluation of intra- and inter-assay variability and test-retest analysis in a subset of randomly chosen participants. An additional sample of urine or blood was collected from these participants, and these samples were handled in the same manner as the original ones, locally and at the central laboratory. Reliability was assessed with the intraclass correlation coefficient (ICC), estimated through a random effects model. Coefficients of variation (CV) and Bland-Altman plots were additionally used to assess measurement variability. Laboratory intra and inter-assay CVs varied from 0.86% to 7.77%. From test-retest analyses, the ICCs were high for the majority of the analytes. Notably lower ICCs were observed for serum sodium (ICC=0.50; 95%CI=0.31-0.65) and serum potassium (ICC=0.73; 95%CI=0.60-0.83), due to the small biological range of these analytes. The CVs ranged from 1 to 14%. The Bland-Altman plots confirmed these results. The quality control analyses showed that the collection, processing and measurement protocols utilized in the ELSA-Brasil produced reliable biochemical measurements.
authors.affiliation: Programa de Pós Graduação em Epidemiologia, Faculdade de Medicina e Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: R
authors.initials: R
authors.lastname: Ladwig
authors.affiliation: Programa de Pós Graduação em Epidemiologia, Faculdade de Medicina e Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: A
authors.initials: A
authors.lastname: Vigo
authors.affiliation: Laboratório Clínico, Hospital Universitário, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: L M G
authors.initials: LM
authors.lastname: Fedeli
authors.affiliation: Department of Biostatistics, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: L E
authors.initials: LE
authors.lastname: Chambless
authors.affiliation: Departamento de Clínica Médica, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: I
authors.initials: I
authors.lastname: Bensenor
authors.affiliation: Programa de Pós Graduação em Epidemiologia, Faculdade de Medicina e Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: M I
authors.initials: MI
authors.lastname: Schmidt
authors.affiliation: Departamento de Propedêutica Complementar, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
authors.forename: P G
authors.initials: PG
authors.lastname: Vidigal
authors.affiliation: Programa de Pós Graduação em Epidemiologia, Faculdade de Medicina e Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: C D
authors.initials: CD
authors.lastname: Castilhos
authors.affiliation: Programa de Pós Graduação em Epidemiologia, Faculdade de Medicina e Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: B B
authors.initials: BB
authors.lastname: Duncan
mesh_terms: D000328:Adult; D001938:Brazil; D006801:Humans; D007753:Laboratories / Q000592:standards*; D008137:Longitudinal Studies; D015588:Observer Variation; D011786:Quality Control; D012015:Reference Standards; D015203:Reproducibility of Results