title: Should I repeat my 1:2s QC rejection?
abstract: BACKGROUND
  Repeating a QC that is outside 2SD from the mean (1:2s rule) appears to be a common practice. Although this form of repeat sampling is frowned on by many, the comparative power of the approach has not been formally evaluated.
  
  
  METHODS
  We computed power functions mathematically and by computer simulation for 4 different 1:2s repeat-sampling strategies, as well as the 1:2s rule, the 1:3s rule, and 2 common QC multirules.
  
  
  RESULTS
  The false-rejection rates for the repeat-sampling strategies were similarly low to those of the 1:3s QC rule. The error detection rates for the repeat-sampling strategies approached those of the 1:2s QC rule for moderate to large out-of-control error conditions. In most cases, the power of the repeat-sampling strategies was superior to the power of the QC multirules we evaluated. The increase in QC utilization rate ranged from 4% to 13% for the repeat-sampling strategies investigated.
  
  
  CONCLUSIONS
  The repeat-sampling strategies provide an effective tactic to take advantage of the desirable properties of both the 1:2s and 1:3s QC rules. Additionally, the power of the repeat-sampling strategies compares favorably with the power of 2 common QC multirules. These improvements come with a modest increase in the average number of controls tested.
authors.affiliation: Bio-Rad Laboratories, Quality Systems Division, Plano, TX 75074, USA. curtis_parvin@bio-rad.com
authors.forename: Curtis A
authors.initials: CA
authors.lastname: Parvin
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Kuchipudi
authors.forename: John C
authors.initials: JC
authors.lastname: Yundt-Pacheco
mesh_terms: D019411:Clinical Laboratory Techniques / Q000592:standards*; D006801:Humans; D011336:Probability; D011785:Quality Assurance, Health Care; D011786:Quality Control