title: Urine TGF- beta1 assay validation: spinning down urine samples could diminish TGF-beta1 signal.
abstract: BACKGROUND
  TGF-beta1 is a mediator of immune and anti-inflammatory responses. The present research was dedicated to the validation of the urine Quantikine Human TGF-beta1 ELISA assay.
  
  
  METHODS
  A reference interval was developed utilizing 100 urine samples from healthy donors. Samples containing precipitate were centrifuged and supernatants or un-spun specimens were run with TGF-beta1 assay.
  
  
  RESULTS
  Supernatant TGF-beta1 concentrations are only a fraction of the un-spun sample values (77% to 29%, even less for the low concentration samples). Validation involving un-centrifuged urine samples demonstrated the following TGF-beta1 assay characteristics: linearity from 23 to 1286 pg/mL, recovery from 95 to 116%; precision: < 17%; analytical specificity 3 pg/mL; reference interval from 0 to 39 pg/mg creatinine; freeze-thaw stability: after first thawing, urine samples could loose from 5 to 40% of TGF-beta1 activity on each following freeze-thaw circle.
  
  
  CONCLUSIONS
  For TGF-beta1 assay, urine sample preparation should not include a centrifugation step; repeating freeze-thawing should be avoided.
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84108, USA. igor.pavlov@aruplab.com
authors.forename: Igor Y
authors.initials: IY
authors.lastname: Pavlov
authors.forename: Fuad
authors.initials: F
authors.lastname: Shihab
authors.forename: Julio C
authors.initials: JC
authors.lastname: Delgado
mesh_terms: D016477:Artifacts; D002498:Centrifugation; D011232:Chemical Precipitation; D015925:Cryopreservation; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D011309:Preservation, Biological; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000379:methods*; D053773:Transforming Growth Factor beta1 / Q000652:urine*; D016482:Urinalysis / Q000379:methods*
chemical_list: D011933:Reagent Kits, Diagnostic; D053773:Transforming Growth Factor beta1