title: Factors affecting urinary myoglobin stability in vitro.
abstract: Urine myoglobin concentrations are measured clinically to assess rhabdomyolysis and the related risk of renal damage. We studied urine myoglobin concentrations in vitro to explore the factors affecting stability. Myoglobin was very unstable in urine specimens, especially below pH 6.5, and its immunoreactivity deteriorated rapidly with increasing temperatures. The deterioration rate was influenced greatly by urine myoglobin concentration, suggesting rate-limiting kinetics. Myoglobin in acidic phosphate-buffered saline was significantly more stable than in acidic urine, indicating that urinary factors in addition to pH are involved in myoglobin instability. These unidentified urinary factors had a molecular weight of less than 10 kd. Our results provide additional insight into the mechanism involved in the instability of the urine myoglobin concentration. Understanding the stability of myoglobin in the preanalytic in vitro phase and its potential in vivo instability is essential in assuring the reliability and clinical usefulness of urine myoglobin measurements.
authors.affiliation: Department of Laboratory Medicine, University of Washington School of Medicine, Seattle 98105, USA.
authors.forename: Zehava
authors.initials: Z
authors.lastname: Chen-Levy
authors.forename: Mark H
authors.initials: MH
authors.lastname: Wener
authors.forename: Bert
authors.initials: B
authors.lastname: Toivola
authors.forename: Phyllis
authors.initials: P
authors.lastname: Daum
authors.forename: Morayma
authors.initials: M
authors.lastname: Reyes
authors.forename: James S
authors.initials: JS
authors.lastname: Fine
mesh_terms: D016477:Artifacts; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007124:Immunoenzyme Techniques; D066298:In Vitro Techniques; D009211:Myoglobin / Q000032:analysis*; D009212:Myoglobinuria / Q000175:diagnosis / Q000652:urine*; D009391:Nephelometry and Turbidimetry; D011863:Radioimmunoassay; D012016:Reference Values; D012206:Rhabdomyolysis / Q000175:diagnosis / Q000652:urine; D013048:Specimen Handling / Q000379:methods*
chemical_list: D009211:Myoglobin