title: External quality assurance of fibrinogen assays using normal plasma: results of the 2008 College of American Pathologists proficiency testing program in coagulation.
abstract: BACKGROUND
  Proper diagnosis and therapy of fibrinogen deficiency requires high-quality fibrinogen assays.
  
  
  OBJECTIVE
  To assess the interlaboratory bias, precision, and grading of fibrinogen assays used by laboratories participating in the United States College of American Pathologists proficiency testing program in coagulation.
  
  
  METHODS
  Two identical vials of normal plasma were sent to more than 3500 laboratories. Participants measured fibrinogen levels using local methods.
  
  
  RESULTS
  Fifty different fibrinogen methods were evaluated. All-method bias was 8.3% (range of method-specific biases, 0.0%-27.0%) and all-method coefficient of variation was 7.7% (range of method-specific coefficients of variation, 0.7%-25.8%). After controlling for reagent/instrument type, mean fibrinogen levels were 11.6% higher for prothrombin time-based reagents compared to Clauss (P < .001), and coefficient of variation was 46% lower for mechanical endpoint instruments compared to photo-optical. Most testing events (97.4%) could be reliably graded as pass or fail using a target range of ±20% from the method mean (total pass rate, 98.8%). Total fail rate was 3.0-fold lower for mechanical instruments compared to photo-optical (0.5% versus 1.5%, P  =  .001). Nonetheless many photo-optical methods had very high precision and very low fail rates.
  
  
  CONCLUSIONS
  Fibrinogen assays showed highly variable methodology and performance characteristics. Bias, precision, and grading were affected by the type of reagent or instrument used.
authors: Department of Pathology, University of Kansas Medical Center, Kansas City, USA. mcunningham@kumc.edu
authors: Mark T
authors: MT
authors: Cunningham
authors: John D
authors: JD
authors: Olson
authors: Wayne L
authors: WL
authors: Chandler
authors: Elizabeth M
authors: EM
authors: Van Cott
authors: Charles S
authors: CS
authors: Eby
authors: Jun
authors: J
authors: Teruya
authors: Sandra C
authors: SC
authors: Hollensead
authors: Dorothy M
authors: DM
authors: Adcock
authors: Paul M
authors: PM
authors: Allison
authors: Kandice K
authors: KK
authors: Kottke-Marchant
authors: Marc D
authors: MD
authors: Smith
mesh_terms: D001777:Blood Coagulation; D005340:Fibrinogen / Q000032:analysis*; D006801:Humans; D007753:Laboratories / Q000592:standards*; D010338:Pathology, Clinical / Q000592:standards*; D011785:Quality Assurance, Health Care / Q000592:standards*
chemical_list: D005340:Fibrinogen