title: Recovery of microarray-quality RNA from frozen EDTA blood samples.
abstract: BACKGROUND
  The availability of blood collection systems with RNA stabilizing additives (e.g. PAXgene) has opened the field for gene expression profiling in large multi-center clinical trials. Here, we investigated whether the PAXgene system also offers a method for extraction of RNA from frozen EDTA blood samples, which do not yield RNA of high enough quality for RNA expression profiling, when extracted with standard protocols.
  
  
  METHODS
  Whole blood was obtained from six healthy volunteers in conventional EDTA tubes and frozen. The thawed EDTA blood was transferred into PAXgene tubes, and the RNA was extracted using the PAXgene RNA extraction kit. Microarray analysis was performed to asses the effect of RNA quality on gene expression profiles.
  
  
  RESULTS
  The RNA yield of the transferred samples was 1.76+/-0.88 microg/ml. This yield was clearly lower than the yield from a PAXgene reference group (2.84+/-0.62 microg/ml), but considerably higher than the yield resulting from a standard protocol usually applied to fresh EDTA blood samples (0.07+/-0.06 microg/ml). The RNA integrity number (RIN) of the transferred samples was 6.1+/-0.8 as compared to 9.8+/-0.1 for the PAXgene reference. Microarray analysis of the extracted RNA suggested that samples with RIN values above 5 produce data that fulfill the quality criteria defined by the manufacturer.
  
  
  CONCLUSIONS
  The transfer of thawed EDTA blood into PAXgene blood collection tubes offers a method to recover sufficient RNA of acceptable quality for microarray experiments.
authors.affiliation: Clinical Pharmacology, Bayer Schering Pharma AG, Berlin, Germany. johanna.beekman@bayerhealthcare.com
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Beekman
authors.forename: Joachim
authors.initials: J
authors.lastname: Reischl
authors.forename: David
authors.initials: D
authors.lastname: Henderson
authors.forename: David
authors.initials: D
authors.lastname: Bauer
authors.forename: Rainer
authors.initials: R
authors.lastname: Ternes
authors.forename: Carol
authors.initials: C
authors.lastname: Peña
authors.forename: Chetan
authors.initials: C
authors.lastname: Lathia
authors.forename: Jürgen F
authors.initials: JF
authors.lastname: Heubach
mesh_terms: D000328:Adult; D001793:Blood Preservation / Q000379:methods*; D001800:Blood Specimen Collection / Q000379:methods; D004492:Edetic Acid / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D008957:Models, Genetic; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D011786:Quality Control; D012313:RNA / Q000097:blood / Q000235:genetics / Q000302:isolation & purification*; D013048:Specimen Handling / Q000295:instrumentation / Q000379:methods
chemical_list: D012313:RNA; D004492:Edetic Acid