Investigating optimum sample preparation for infrared spectroscopic serum diagnostics

Biofluids, such as serum and plasma, represent an ideal medium for the diagnosis of disease due to their ease of collection, that can be performed worldwide, and their fundamental involvement in human function. The ability to diagnose disease rapidly with high sensitivity and specificity is essential to exploit advances in new treatments, in addition the ability to rapidly profile disease without the need for large scale medical equipment (e.g. MRI, CT) would enable closer patient monitoring with reductions in mortality and morbidity. Due to these reasons vibrational spectroscopy has been investigated as a diagnostic tool and has shown great promise for serum spectroscopic diagnostics. However, the optimum sample preparation, optimum sampling mode and the effect of sample preparation on the serum spectrum are unknown. This paper examines repeatability and reproducibility of attenuated total reflection (ATR) compared to transmission sampling modes and their associated serum sample preparation with spectral standard deviation of 0.0015 (post pre-processing) achievable for both sampling modes proving the collection of robust spectra. In addition this paper investigates the optimum serum sample dilution factor for use in high throughput transmission mode analysis with a 3-fold dilution proving optimum and shows the use of ATR and transmission mode spectroscopy to illuminate similar discriminatory differences in a patient study. These fundamental studies provide proof of robust spectral collection that will be required to enable clinical translation of serum spectroscopic diagnostics