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- 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.
- Authors
Tiselius, Hans-Göran
- Abstract
The purpose of this study is to derive approximate estimates of ion-activity products of CaOx (AP) and CaP (AP) 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) and AP(CaP) by using urine concentrations of the most important determinants of AP and AP. 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) index was obtained with the following formula ( r = 0.99; p = 0.0000): $${\text{AP(CaOx)index}}_{\text{CONC}} = \frac{{2.09 \times c{Ca}^{0.84} \times c{Ox} }}{{c{Cit}^{0.22} \times c{Mg}^{0.12}}}. $$ The corresponding formula for AP (CaP) index was derived from comparison with the corresponding calculations of AP(CaP) index in 24 h urine ( r = 0.91; p = 0.0000): $${\text{AP(CaP)index}}_{\text{CONC}} = \frac{{0.432 \times c{Ca}^{1.07} \times c{P}^{0.70} \times ({pH} - 4.5)^{6.8}}}{{c{Cit}^{0.20} }}. $$ The proposed simplified formulas enable calculation of approximate estimates of AP and AP 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.
- Subjects
CALCIUM phosphate; CALCIUM oxalate; HYDROGEN-ion concentration; URINARY calculi; KIDNEY diseases
- Publication
Urolithiasis, 2013, Vol 41, Issue 2, p105
- ISSN
2194-7228
- Publication type
Article
- DOI
10.1007/s00240-012-0524-9