title: A simplified estimate of the ion-activity product of calcium phosphate in urine.
abstract: A computerized program was used to calculate the activities of the calcium, phosphate, and hydrogen phosphate ions. The most important determinants for ion-activity products of calcium phosphate and brushite were calcium, phosphate, citrate, urine volume, and pH. These urine variables were used to derive indices corresponding to ion-activity products of calcium phosphate (AP[CaP] index) and calcium hydrogen phosphate (AP[Bru] index). Factors were given to adapt these indices to collection periods shorter than 24 h. Relationships between the AP(CaP) index and ion-activity products of hydroxyapatite and octacalcium phosphate were also formulated. With urine electrolytes within the normal range a very good correlation was obtained between these indices and corresponding ion-activity products. The coefficient of correlation was better than 0.99. The presented indices might be useful in the evaluation of patients with renal calcium stone formation.
mesh_terms: D002130:Calcium Phosphates / Q000652:urine*; D003201:Computers; D003460:Crystallization; D004573:Electrolytes / Q000652:urine; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012984:Software; D014545:Urinary Calculi / Q000652:urine*
chemical_list: D002130:Calcium Phosphates; D004573:Electrolytes; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous