title: A novel bio-assay increases the detection yield of microbiological impurity of dialysis fluid, in comparison to the LAL-test.
abstract: BACKGROUND
  Biological purity of dialysis water is considered as one of the primary conditions to deliver optimal haemodialysis.
  
  
  METHODS
  The present study explores the added value of a novel cytokine (IL-1ss) induction assay, using a monocytic THP-1 cell line, compared to the classical detection methods for microbial dialysis fluid contaminants.
  
  
  RESULTS
  In contrast to the Limulus Amebocyte Lysate (LAL)-test, which only detects intact lipopolysaccharide (LPS), the THP-1 assay was also sensitive to peptidoglycan, short bacterial DNA fragments and LPS fragments <5 kD. The purity of 269 dialysis fluid samples was tested by the THP-1 assay and compared to the LAL-test. Two hundred and sixty samples complied with the definition of 'pure' dialysis fluid as laid down in the European Pharmacopeia (European Best Practice Guidelines for Hemodialysis. Section IV. Dialysis fluid purity. Nephrol Dial Transplant 2002; 17: 45-62) but 27 of these so-called pure dialysates (10.3%) provoked a pro-inflammatory response in the THP-1 assay. Furthermore, among the 230 samples that complied the definition of an ultrapure dialysis fluid, 21 samples (9.1%) were pro-inflammatory. These data illustrate that this novel bio-assay detects microbiological entities with an inflammatory potential that cannot be found by the classical LAL screening method.
  
  
  CONCLUSIONS
  Adding this novel THP-1 assay to the classical methods will be helpful in the prevention of biofilm formation in the delivery system and should have relevance by more accurate detection of dialysate contamination, hence decreasing micro-inflammation in the haemodialysis patient.
authors.affiliation: Department of Internal Medicine, Renal Division, Ghent University Hospital, Gent, Belgium. griet.glorieux@UGent.be
authors.forename: Griet
authors.initials: G
authors.lastname: Glorieux
authors.forename: Eva
authors.initials: E
authors.lastname: Schepers
authors.forename: Ralf
authors.initials: R
authors.lastname: Schindler
authors.forename: Horst-Dieter
authors.initials: HD
authors.lastname: Lemke
authors.forename: Francis
authors.initials: F
authors.lastname: Verbeke
authors.forename: Annemieke
authors.initials: A
authors.lastname: Dhondt
authors.forename: Norbert
authors.initials: N
authors.lastname: Lameire
authors.forename: Raymond
authors.initials: R
authors.lastname: Vanholder