title: Measurement of the risk of calcium phosphate crystallization in urine.
abstract: A method is described for analysis of the risk of calcium phosphate (CaP) crystallization in urine samples. The pH required for formation of 500 crystals in the size range 3.5 to 5 micron (pHCaP) was determined in a Coulter Counter following addition of sodium hydroxide. The risk of CaP crystallization (CaP-CR) was defined as: 1/(pHCaP--5.8). CaP-CR was determined in 24 h urine collections from 25 patients with calcium stone disease and 26 normal subjects, each urine diluted to a creatinine concentration of 5 mumol per ml. The mean (+/- SD) CaP-CR was 0.71 +/- 0.18 and 0.63 +/- 0.14 respectively and did not differ significantly. This method might be useful for evaluations and follow-up of stone formers with respect to the risk of CaP precipitation and stone formation.
mesh_terms: D002130:Calcium Phosphates / Q000652:urine*; D003460:Crystallization; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008851:Micropore Filters; D010316:Particle Size; D012306:Risk; D014545:Urinary Calculi / Q000032:analysis*
chemical_list: D002130:Calcium Phosphates; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous