title: The Importance of Reagent Lot Registration in External Quality Assurance/Proficiency Testing Schemes.
abstract: Providers of external quality assurance (EQA)/proficiency testing schemes have traditionally focused on evaluation of measurement procedures and participant performance and little attention has been given to reagent lot variation. The aim of the present study was to show the importance of reagent lot registration and evaluation in EQA schemes.
  
  
  
  Results from the Noklus (Norwegian Quality Improvement of Primary Care Laboratories) urine albumin/creatinine ratio (ACR) and prothrombin time international normalized ratio (INR) point-of-care EQA schemes from 2009-2015 were used as examples in this study.
  
  
  
  The between-participant CV for Afinion ACR increased from 6%-7% to 11% in 3 consecutive surveys. This increase was caused by differences between albumin reagent lots that were also observed when fresh urine samples were used. For the INR scheme, the CoaguChek INR results increased with the production date of the reagent lots, with reagent lot medians increasing from 2.0 to 2.5 INR and from 2.7 to 3.3 INR (from the oldest to the newest reagent lot) for 2 control levels, respectively. These differences in lot medians were not observed when native patient samples were used.
  
  
  
  Presenting results from different reagent lots in EQA feedback reports can give helpful information to the participants that may explain their deviant EQA results. Information regarding whether the reagent lot differences found in the schemes can affect patient samples is important and should be communicated to the participants as well as to the manufacturers. EQA providers should consider registering and evaluating results from reagent lots.
authors.affiliation: The Norwegian Quality Improvement of Primary Care Laboratories (Noklus), Haraldsplass Deaconess Hospital, Bergen, Norway; anne.stavelin@noklus.no.
authors.forename: Anne
authors.initials: A
authors.lastname: Stavelin
authors.affiliation: The Norwegian Quality Improvement of Primary Care Laboratories (Noklus), Haraldsplass Deaconess Hospital, Bergen, Norway;
authors.forename: Berit Oddny
authors.initials: BO
authors.lastname: Riksheim
authors.affiliation: The Norwegian Quality Improvement of Primary Care Laboratories (Noklus), Haraldsplass Deaconess Hospital, Bergen, Norway;
authors.forename: Nina Gade
authors.initials: NG
authors.lastname: Christensen
authors.affiliation: The Norwegian Quality Improvement of Primary Care Laboratories (Noklus), Haraldsplass Deaconess Hospital, Bergen, Norway; Department of Public Health and Primary Health Care, Faculty of Medicine and Dentistry, University of Bergen, Bergen, Norway.
authors.forename: Sverre
authors.initials: S
authors.lastname: Sandberg
mesh_terms: D000418:Albumins / Q000032:analysis; D003404:Creatinine / Q000652:urine; D006801:Humans; D007202:Indicators and Reagents / Q000592:standards*; D019934:International Normalized Ratio; D059021:Laboratory Proficiency Testing; D019095:Point-of-Care Systems; D011517:Prothrombin Time; D011785:Quality Assurance, Health Care; D011933:Reagent Kits, Diagnostic
chemical_list: D000418:Albumins; D007202:Indicators and Reagents; D011933:Reagent Kits, Diagnostic; D003404:Creatinine