[Studies on the crystallization tendency of calcium oxalate in urine--a study of experimental and computer-assisted determination of the risk of urinary calculi formation].

In this study a method o the semiquantitative determination of the crystallization tendency for calcium oxalate in urine is described. It is based on the addition of a well-defined amount of ammonium oxalate (31.3 nmol) to a urine sample (30 ml). The so caused clouding of the urine is measured by a photometer 20 min later. The method guarantees an acceptable reproducibility and is simple to be performed in each clinical laboratory. The results of mathematical correlation and discriminant analysis show that the calcium concentration influences the crystallization of calcium oxalate as most of all urinary constituents. Furthermore, evidence of a high specificity of the method is given by a reclassification rate of about 80% in the discriminant analytical computation.