title: Performance of electrolyte measurements assessed by a trueness verification program.
abstract: BACKGROUND
  In this study, we analyzed frozen sera with known commutabilities for standardization of serum electrolyte measurements in China.
  
  
  METHODS
  Fresh frozen sera were sent to 187 clinical laboratories in China for measurement of four electrolytes (sodium, potassium, calcium, and magnesium). Target values were assigned by two reference laboratories. Precision (CV), trueness (bias), and accuracy [total error (TEa)] were used to evaluate measurement performance, and the tolerance limit derived from the biological variation was used as the evaluation criterion.
  
  
  RESULTS
  About half of the laboratories used a homogeneous system (same manufacturer for instrument, reagent and calibrator) for calcium and magnesium measurement, and more than 80% of laboratories used a homogeneous system for sodium and potassium measurement. More laboratories met the tolerance limit of imprecision (coefficient of variation [CVa]) than the tolerance limits of trueness (biasa) and TEa. For sodium, calcium, and magnesium, the minimal performance criterion derived from biological variation was used, and the pass rates for total error were approximately equal to the bias (<50%). For potassium, the pass rates for CV and TE were more than 90%. Compared with the non homogeneous system, the homogeneous system was superior for all three quality specifications.
  
  
  CONCLUSIONS
  The use of commutable proficiency testing/external quality assessment (PT/EQA) samples with values assigned by reference methods can monitor performance and provide reliable data for improving the performance of laboratory electrolyte measurement. The homogeneous systems were superior to the non homogeneous systems, whereas accuracy of assigned values of calibrators and assay stability remained challenges.
authors.forename: Menglei
authors.initials: M
authors.lastname: Ge
authors.forename: Haijian
authors.initials: H
authors.lastname: Zhao
authors.forename: Ying
authors.initials: Y
authors.lastname: Yan
authors.forename: Tianjiao
authors.initials: T
authors.lastname: Zhang
authors.forename: Jie
authors.initials: J
authors.lastname: Zeng
authors.forename: Weiyan
authors.initials: W
authors.lastname: Zhou
authors.forename: Yufei
authors.initials: Y
authors.lastname: Wang
authors.forename: Qinghui
authors.initials: Q
authors.lastname: Meng
authors.forename: Chuanbao
authors.initials: C
authors.lastname: Zhang
mesh_terms: D002118:Calcium / Q000097:blood; D002681:China; D019411:Clinical Laboratory Techniques / Q000592:standards*; D004573:Electrolytes / Q000097:blood*; D006801:Humans; D008274:Magnesium / Q000097:blood; D011188:Potassium / Q000097:blood; D012964:Sodium / Q000097:blood
chemical_list: D004573:Electrolytes; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium