Colorimetric and visual evaluation of sarcosine in the artificial urine

Suitable molecular or biochemical markers are sought for rapid diagnostics of cancer. A very promising candidate is the sarcosine (SAR) amino acid, which is elevated in the urine of the patients with prostate cancer. The aim of this work was to develop a simple, fast and reliable method for SAR detection in human urine. Sarcosine oxidase hydrolyses sarcosine and the resulting peroxide is converted to a colored product. By colorimetric analysis, sarcosine could be detected at low concentrations, limit of detection (LOD) was 1 µM and limit of quantification (LOQ) was 6 µM in artificial urine. As a quick test for the presence of sarcosine in urine, a visual assessment of color change has been proposed. Visual results were evaluated as RGB signal densities. The obtained results show that the average RGB variability between test samples was about 10 %. From these values, the ROC curve of the individual experiments was determined. Sensitivity (from 0.59 to 0.83) and specificity (1.00) were calculated using ROC curves according to the type of artificial urine. ROC curves were more than 25 % rated as excellent, 65 % as very good from 5% as good and none as unsatisfactory. Conclusion: Colorimetric detection of sarcosine in urine was sensitive. Visual evaluation of the test showed 100% success in identifying the presence of sarcosine in artificial urine. The obtained data show the potential of the method for the visual evaluation of the presence of sarcosine in the urine and its possible use in the diagnostics of prostate cancer.