Background: We aimed to develop a new simplified method to determine the urinary calcium-oxalate saturation.
Methods: The ion-activity product (AP) of urinary calcium oxalate was estimated in 345 clinical urine specimens (all 2.5 hour collections) using the Equil2 computer program and several other methods, and the results were compared. A new index using 4 parameters was created using multiple regression analysis.
Results: Our new simplified method (the AP(CaOx) index EQ2) provided a better approximation to the Equil2 method (r = 0.9897) than other conventional methods.
Conclusion: This new method requiring 4 factors (urinary calcium, magnesium, oxalate, and citrate concentrations) is simple and clinically usable.