title: A proposed method for approximate estimates of the ion-activity products of calcium oxalate and calcium phosphate in spot-urine samples or in urine samples collected during less well defined periods of time.
abstract: The purpose of this study is to derive approximate estimates of ion-activity products of CaOx (APCaOx) and CaP (APCaP) useful for spot urine or other less well defined short-term urine collections. In accordance with previously applied and described principles for estimating ion-activity products, the intention was to derive simplified estimates of AP(CaOx)CONC and AP(CaP)CONC by using urine concentrations of the most important determinants of APCaOx and APCaP. A comparison thus was made between estimates derived in that manner and AP(CaOx) index and AP(CaP) index obtained from calculations based on analysis of 24 h urine samples. The best fit between estimates of AP(CaOx) index in 24 h urine and AP(CaOx) indexCONC was obtained with the following formula (r = 0.99; p = 0.0000): [Formula in text] The corresponding formula for AP (CaP) indexCONC was derived from comparison with the corresponding calculations of AP(CaP) index in 24 h urine (r = 0.91; p = 0.0000): [Formula in text] The proposed simplified formulas enable calculation of approximate estimates of APCaOx and APCaP in spot-urine samples or any kind of urine collection for which duration of the collection period is less well known and by using the concentrations (c) of the variables in mmol/L in the two formulas.
authors.affiliation: Division of Urology, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden. hans.tiselius@karolinska.se
authors.forename: Hans-Göran
authors.initials: HG
authors.lastname: Tiselius
mesh_terms: D002129:Calcium Oxalate / Q000737:chemistry / Q000652:urine*; D002130:Calcium Phosphates / Q000737:chemistry / Q000652:urine*; D003460:Crystallization; D006801:Humans; D009994:Osmolar Concentration; D012307:Risk Factors; D013997:Time Factors; D016482:Urinalysis / Q000379:methods* / Q000706:statistics & numerical data; D014545:Urinary Calculi / Q000737:chemistry* / Q000209:etiology
chemical_list: D002130:Calcium Phosphates; D002129:Calcium Oxalate; C020243:calcium phosphate