A system of interpretation of infrared spectra of calculi for routine use in the clinical laboratory.

We have devised systematic schemes for objectives qualitative analysis of the IR spectra of calculi. These schemes are presented as flow charts based on questions each requiring a yes or no answer before going on to the next step. The specific question asked in each step concerns the similarity of a limited region of the spectrum to reference spectra. For renal calculi, 5 regions are evaluated and a maximum of 10 decisions is necessary to complete the analysis. Biliary calculi are treated similarily, with 5 spectral regions evaluated and a maximum of 8 yes-no decisions required. The method requires less technician time and is much less susceptible to differences in subjective judgment than the wet chemical procedure. Three percent of stones contain unusual components and are quickly recognized as such and identified using a library of reference spectra.