title: Solution densities and estimated total protein contents associated with inappropriate flotation of separator gel in different blood collection tubes.
abstract: BACKGROUND
  Clinical samples that have densities greater than that of separator gel in specimen tubes may exhibit gel flotation to the top of the specimen upon centrifugation. Inappropriate separator gel flotation can occur in specimens with high protein content. In automated analytical systems, gel flotation can lead to mechanical disruption and potential inaccurate result reporting upon aspiration into instrument sampling probes.
  
  
  OBJECTIVE
  To determine the relative specimen densities and estimated total protein contents at which specimen gel flotation would occur upon centrifugation in commonly used commercial specimen tubes, a comparative study of separator gel density was initiated using prepared dextran solutions.
  
  
  METHODS
  Specific gravity of several dextran solutions was determined by direct hydrometry. The dextran solutions were introduced to serum and plasma lithium heparin BD Vacutainer specimen tubes manufactured by Becton, Dickinson and Company and into Vacuette specimen tubes manufactured by Greiner Bio-One containing separator gel. Following centrifugation the specimen tubes were examined for gel flotation.
  
  
  RESULTS
  Flotation was observed at a lower dextran solution density for Greiner than for BD tubes in both serum and plasma separator gel specimen tubes. Additionally, some differences between specimen tube lots were observed for both BD and Greiner tubes. The total protein content in clinical samples that would result in gel flotation can be estimated for different specimen container types.
  
  
  CONCLUSIONS
  Differences were observed for the gel separator specific gravity in different blood collection containers. Laboratories wishing to avoid problems with inappropriate gel flotation in high protein samples should consider these observations.
authors: Clinical Laboratory, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
authors: Ronald C
authors: RC
authors: Faught
authors: James
authors: J
authors: Marshall
authors: Joshua
authors: J
authors: Bornhorst
mesh_terms: D001798:Blood Proteins / Q000032:analysis*; D001800:Blood Specimen Collection / Q000379:methods*; D002499:Centrifugation, Density Gradient; D003911:Dextrans; D005782:Gels; D006801:Humans; D012996:Solutions; D013046:Specific Gravity; D013048:Specimen Handling / Q000379:methods*
chemical_list: D001798:Blood Proteins; D003911:Dextrans; D005782:Gels; D012996:Solutions