Comparison of methods and guaranteeing quality of analyses of urinary calculi--5th international ring test

For five samples of our 5th international ring test for the quality control of methods of urinary calculus analysis we received 46 results from 19 countries obtained by means of ten different methods. The mean standard of quality (SQ) for all participants with quantitative methods is 2.11. Most laboratories employed X-ray diffraction (n = 21; SQ = 2.09) for quantitative calculus analysis. The mean deviation (delta x) per component from the ideal composition is fortunately low--about 0.10 molar parts for all participants, 0.06 molar parts for X-ray and infrared spectroscopy technique together. From the aspect of accuracy, the physical methods of analysis, X-ray diffraction and IR spectrophotometry, are clearly superior to all other analytical techniques.