title: Predicted effects of proposed tightened acceptance criterion for Pb proficiency testing (PT) on PT sample pass rates for Pb point-of-care testing.
abstract: BACKGROUND
  There is current advocacy for change in Pb proficiency testing (PT) acceptance criterion from ± 4 μg/dl ([Pb] <40 μg/dl; criterion a) to ± 2 μg/dl ([Pb] <20 μg/dl, criterion b). We examined the effect of this proposed change on PT sample pass rates for point-of-care testing (POCT) as predicted by imprecision of POCT PT sample results.
  
  
  METHODS
  Inter-site standard deviations (s) of POCT PT results were tabulated as a function of [Pb] and characterized as a linear function of [Pb] (r(2)>0.8). Given s, predicted minimum, random-error-only PT failure rates (Fp) as a function of [Pb] were computed as the fraction of a normal distribution of results ([Pb]± s) that would fall outside of boundaries of acceptance criterion a or b.
  
  
  RESULTS
  For [Pb]=2-20 μg/dl, current observed PT sample failure rates using criterion a range from 3 to 6%, which are greater than the predicted minimum failure rates based on s alone (Fp(a)=0-6%). In contrast, predicted minimum failure rates based on s using criterion b are greatly increased (Fp(b)=5-35%).
  
  
  CONCLUSIONS
  Given the degree of inter-site imprecision among POCT Pb PT results, adoption of criterion b for PT acceptance will dramatically increase Pb PT sample failure rates for POCT due to random-error alone.
authors.affiliation: Department of Pathology, Jefferson University Hospitals, Philadelphia, PA, United States.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: McCloskey
authors.forename: Bryon P
authors.initials: BP
authors.lastname: Jackson
authors.forename: Frank R
authors.initials: FR
authors.lastname: Bordash
authors.forename: Kathy J
authors.initials: KJ
authors.lastname: Ubben
authors.forename: James D
authors.initials: JD
authors.lastname: Landmark
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Stickle
mesh_terms: D006801:Humans; D007854:Lead / Q000097:blood*; D019095:Point-of-Care Systems; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D007854:Lead