title: Comparison between bottom-up and top-down approaches in the estimation of measurement uncertainty.
abstract: BACKGROUND
  Measurement uncertainty is a metrological concept to quantify the variability of measurement results. There are two approaches to estimate measurement uncertainty. In this study, we sought to provide practical and detailed examples of the two approaches and compare the bottom-up and top-down approaches to estimating measurement uncertainty.
  
  
  METHODS
  We estimated measurement uncertainty of the concentration of glucose according to CLSI EP29-A guideline. Two different approaches were used. First, we performed a bottom-up approach. We identified the sources of uncertainty and made an uncertainty budget and assessed the measurement functions. We determined the uncertainties of each element and combined them. Second, we performed a top-down approach using internal quality control (IQC) data for 6 months. Then, we estimated and corrected systematic bias using certified reference material of glucose (NIST SRM 965b).
  
  
  RESULTS
  The expanded uncertainties at the low glucose concentration (5.57 mmol/L) by the bottom-up approach and top-down approaches were ±0.18 mmol/L and ±0.17 mmol/L, respectively (all k=2). Those at the high glucose concentration (12.77 mmol/L) by the bottom-up and top-down approaches were ±0.34 mmol/L and ±0.36 mmol/L, respectively (all k=2).
  
  
  CONCLUSIONS
  We presented practical and detailed examples for estimating measurement uncertainty by the two approaches. The uncertainties by the bottom-up approach were quite similar to those by the top-down approach. Thus, we demonstrated that the two approaches were approximately equivalent and interchangeable and concluded that clinical laboratories could determine measurement uncertainty by the simpler top-down approach.
authors.forename: Jun Hyung
authors.initials: JH
authors.lastname: Lee
authors.forename: Jee-Hye
authors.initials: JH
authors.lastname: Choi
authors.forename: Jae Saeng
authors.initials: JS
authors.lastname: Youn
authors.forename: Young Joo
authors.initials: YJ
authors.lastname: Cha
authors.forename: Woonheung
authors.initials: W
authors.lastname: Song
authors.forename: Ae Ja
authors.initials: AJ
authors.lastname: Park
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods*; D001786:Blood Glucose / Q000032:analysis*; D006801:Humans; D035501:Uncertainty
chemical_list: D001786:Blood Glucose