title: Effect of freeze/thaw cycles on several biomarkers in urine from patients with kidney disease.
abstract: Urine samples were collected from eleven randomly selected patients with kidney disease, including diabetic nephropathy, chronic nephritis, and nephritic syndrome. Urine samples were treated with one of four protocols for freezing and thawing: freeze directly and thaw directly; freeze directly and thaw by temperature gradient; freeze by temperature gradient and thaw directly; and freeze by temperature gradient and thaw by temperature gradient. After one to six freeze/thaw cycles at -20°C or -80°C, different biomarkers showed differential stabilities. The concentrations of total protein, calcium, and potassium did not change significantly after five freeze/thaw cycles at either -20°C or -80°C. Albumin could only sustain three freeze/thaw cycles at -20°C before it started to degrade. We recommend that urine be stored at -80°C as albumin and the organic ions could sustain five and six freeze/thaw cycles, respectively, using the simple "direct freeze and direct thaw" protocol. Furthermore, in most cases, gradient freeze/thaw cycles are not necessary for urine sample storage.
authors.affiliation: 1 Center for Translational Medicine, Shanghai Key Laboratory of Diabetes, The Metabolic Diseases Biobank, Shanghai Jiao Tong University Affiliated Sixth People's Hospital , Shanghai, China .
authors.forename: Yinan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yi
authors.initials: Y
authors.lastname: Luo
authors.forename: Huijuan
authors.initials: H
authors.lastname: Lu
authors.forename: Niansong
authors.initials: N
authors.lastname: Wang
authors.forename: Yixie
authors.initials: Y
authors.lastname: Shen
authors.forename: Ruihua
authors.initials: R
authors.lastname: Chen
authors.forename: Pingyan
authors.initials: P
authors.lastname: Fang
authors.forename: Hong
authors.initials: H
authors.lastname: Yu
authors.forename: Congrong
authors.initials: C
authors.lastname: Wang
authors.forename: Weiping
authors.initials: W
authors.lastname: Jia
mesh_terms: D015415:Biomarkers / Q000652:urine*; D015925:Cryopreservation / Q000379:methods*; D005615:Freezing; D006801:Humans; D007674:Kidney Diseases / Q000378:metabolism / Q000652:urine*
chemical_list: D015415:Biomarkers