An Exhaustive Review and Experimental Exploration of Clinical Mid-Range FTIR Urine Analysis

Abstract

Urine provides a noninvasive window into the renal and lymphatic systems, providing molecules (potential markers) from around the body that are detectable using mid-range Fourier transform infrared spectroscopy (MR-FTIR). The benefit of MR-FTIR for urine analysis is the simultaneous sampling of many of the 3000+ urine constituents. The highly condensed spectral information in a single drop of urine potentially provides simpler, faster, and cheaper tests for multiple pathologies in a single test, providing hope for simultaneous testing of different pathologies. The shortage of pathologists in the UK and medical experts worldwide motivates research to improve medical diagnostic technologies, increasing interest in techniques like MR-FTIR urine analysis. Clinical MR-FTIR urine analysis is ideally positioned for review, niche enough for an exhaustive progress report, whilst developed enough to highlight challenges and suitable comparison to current approaches. Before clinical spectroscopy can help patients, clinical validation must be demonstrated. The review highlights milestones toward this goal, like replicated or blinded studies. A section is then dedicated to the experimental considerations already investigated, providing a resource for future FTIR urine analysis study design. The paper concludes by testing a critical variable for transmission MR-FTIR spectroscopy, identified by assessment of reviewed references, discussed in only one, urea hydrogen bonding with H2O, emphasizing the importance of robust dehydration protocols for urine MR-FTIR analysis. Academic and industrial collaborators separately duplicated the experiments, increasing confidence in the analysis repeatability and corresponding clinical value of the findings.