title: Stability of urinary thromboxane A2 metabolites and adaptation of the extraction method to small urine volume.
abstract: BACKGROUND
  Thromboxane (TX) A2 is a pro-thrombotic prostanoid synthesized by activated platelets, biotransformed into 11-dehydro-TXB2, measurable in urines. Eleven-dehydro-TXB2 excretion is increased in high risk cardiovascular diseases; however, this cardiovascular biomarker awaits validation in large trials. The need of large urine volume (8 - 10 mL) and the unknown stability of 11-dehydro-TXB2 in urine after collection might limit its implementation.
  
  
  METHODS
  We scaled the original method for urine extraction and 11-dehydro-TXB2 measurement down to 1 mL, and assessed its stability at 4 degrees C or 25 degrees C up to 6 days after collection. The sensitivity of the 1 mL procedure was also tested in aspirin-treated patients with low 11-dehydro-TXB2 excretion
  
  
  RESULTS
  The 1 mL adapted method was highly correlated with the original assay (rho = 0.98, p < 0.001, n = 33). Both methods showed similar recoveries in samples spiked with exogenous 11-dehydro-TXB2. Urinary 11-dehydro-TXB2 values in samples immediately frozen were comparable and highly correlated to values in samples at 4 degrees C (day 6: rho = 0.99, p > 0.001, n = 8) or 25 degrees C (day 6: rho = 0.98, p < 0.001, n = 23) up to 6 days in controls and patients.
  
  
  CONCLUSIONS
  Eleven-dehydro-TXB2 can be measured in small urine volumes and is relatively stable for a few days after collection, even at 25 degrees C. These data allow the validation of this non-invasive cardiovascular biomarker in large studies.
authors.affiliation: Institute of Pharmacology, Catholic University School of Medicine, Rome, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Pagliaccia
authors.affiliation: Department of Biochemistry and Molecular Genetics, American University of Beirut, Beirut, Lebanon.
authors.forename: Aida
authors.initials: A
authors.lastname: Habib
authors.affiliation: Department of Medicine, Catholic University School of Medicine, Rome, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Pitocco
authors.affiliation: Institute of Pharmacology, Catholic University School of Medicine, Rome, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Petrucci
authors.affiliation: Department of Medicine, Catholic University School of Medicine, Rome, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Zaccardi
authors.affiliation: Department of Biochemistry and Clinical Biochemistry, Catholic University School of Medicine, Rome, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Di Stasio
authors.affiliation: Institute of Pharmacology, Catholic University School of Medicine, Rome, Italy.
authors.forename: Bianca
authors.initials: B
authors.lastname: Rocca
mesh_terms: D015925:Cryopreservation; D006801:Humans; D013928:Thromboxane A2 / Q000302:isolation & purification / Q000378:metabolism / Q000652:urine*
chemical_list: D013928:Thromboxane A2