title: Testing for lupus anticoagulants--fresh or frozen?
abstract: BACKGROUND
  There are no previous studies reporting the effect of using frozen-thawed plasma on lupus anticoagulant ratios in kits with the combined screen and confirm assay.
  
  
  METHODS
  In the following study we chose patients with elevated dilute Russel's viper venom test (dRVVT) normalized ratios and compared the test results of fresh to frozen-thawed plasma. Platelet counts ranged from 2 to 7×10(3)/μL (10(9)/L) after a second centrifugation before freezing.
  
  
  RESULTS
  There were 13 out of 14 dRVVT test normalized ratios that decreased after freezing (p<0.001), leading to the misclassification of six of 14 patients with high values that decreased into the reference interval.
  
  
  CONCLUSIONS
  The major finding of this study is that testing frozen-thawed plasma with platelet counts <10,000/μL (10(9)/L) results in a significant decrease in dRVVT ratios. Although there was a consistent decrease in SCT normalized ratios as well, it did not lead to misclassifications.
authors.affiliation: Central Laboratory, Haifa and Western Galilee, Clalit Health Services, Haifa, Israel. paulfr@clalit.org.il
authors.forename: Paul
authors.initials: P
authors.lastname: Froom
authors.forename: Mira
authors.initials: M
authors.lastname: Barak
mesh_terms: D005615:Freezing; D006801:Humans; D016682:Lupus Coagulation Inhibitor / Q000032:analysis*; D010976:Platelet Count; D011517:Prothrombin Time
chemical_list: D016682:Lupus Coagulation Inhibitor