title: Status of serum-calcium and -albumin measurement in Argentina assessed in 300 representative laboratories with 20 fresh frozen single donation sera.
abstract: BACKGROUND
  The Fundación Bioquímica Argentina (FBA) performs external quality assessment (EQA) of >3200 laboratories. However, FBA realizes that sample non-commutability and predominant use of heterogeneous systems may bias the estimated performance and standardization status. To eliminate these confounding factors, a study using frozen single donation sera was undertaken with the focus on serum-calcium and -albumin measurement.
  
  
  METHODS
  Target values were established from the results produced with homogeneous systems. In groups of n=7, system effects were investigated. Laboratory performance was evaluated from the correlation coefficient r between the measurement results for all sera and the target values. This allowed ranking of the laboratories and judgment of the deviation for individual samples (total error) against a 10% limit. The total error specification was a deviation for ≥ 5 samples exceeding 10% and/or causing a result outside the laboratory's reference interval.
  
  
  RESULTS
  For calcium (n=303) (range: 2.06-2.42 mmol/L), 81 laboratories had an r-value <0.6, 43 even <0.4; the total error was relevant for 97 (10% limit) and 111 (reference interval) laboratories. For albumin (n=311) (range: 34.7-45.7 g/L) r was <0.7 (<0.4) in 44 (16) laboratories; 83 and 36 laboratories exceeded the total error criteria. Laboratories using homogeneous systems were generally ranked higher by correlation. System effects were moderate for calcium, but significant for albumin.
  
  
  CONCLUSIONS
  The study demonstrated the need to improve the quality and harmonization of calcium and albumin testing in the investigated laboratories. To achieve this objective, we promote co-operation between laboratories, EQA provider and manufacturers.
authors.affiliation: Laboratory for Analytical Chemistry, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: Hedwig C M
authors.initials: HC
authors.lastname: Stepman
authors.forename: Dietmar
authors.initials: D
authors.lastname: Stöckl
authors.forename: Rosana
authors.initials: R
authors.lastname: Acheme
authors.forename: Sandra
authors.initials: S
authors.lastname: Sesini
authors.forename: Daniel
authors.initials: D
authors.lastname: Mazziotta
authors.forename: Linda M
authors.initials: LM
authors.lastname: Thienpont
mesh_terms: D001118:Argentina; D015982:Bias; D018070:Biological Specimen Banks; D002118:Calcium / Q000097:blood*; D015925:Cryopreservation; D006801:Humans; D007753:Laboratories / Q000592:standards*; D011786:Quality Control; D012016:Reference Values; D015203:Reproducibility of Results; D044967:Serum / Q000737:chemistry*; D012709:Serum Albumin / Q000032:analysis*
chemical_list: D012709:Serum Albumin; D002118:Calcium