PB0174 - The impact of sodium citrate pathology tube additive on Fourier transform infrared reflectance spectroscopy of citrated plasma and the identification of target molecule fibrinogen.

Background: Attenuated total reflectance Fourier transform infrared reflectance spectroscopy (ATR-FTIR) has the potential to provide rapid multivariate analysis of biological samples. However, further understanding is required regarding the impact of pathology tube additives on spectral results and approaches to overcome this.

Aims: We aim to evaluate the impact of sodium citrate additive on the spectra of citrated plasma. Fibrinogen was chosen as a key target control molecule to be identified in the citrated plasma following circumvention of the sodium citrate impact.

Methods: Paired serum and citrated plasma samples were selected from fifteen adults with spare laboratory samples at Northern Pathology Victoria. Spectra were processed in aqueous state in duplicate on the Spectrum 3 (Perkin Elmer) in the mid infrared range (400-4000cm-1) and resolution 4cm-1. The spectral signature of the sodium citrate additive and fibrinogen were measured as a reference. The paired serum samples acted as internal controls, differing from the citrated plasma by the absence of the sodium citrate additive, fibrinogen and other coagulation molecules.

Results: Following baseline correction and second derivitization of the spectra, the sodium citrate additive demonstrated characteristic peaks at 1572 and 1390cm-1 (Figure 1). The dominating effect of sodium citrate was eliminated by excluding these two absorption modes, with the resulting principle component analysis (PCA) model maintaining discrimination between citrated plasma and serum samples. Subsequently, close alignment was demonstrated of the citrated plasma PCA loading marker bands with the measured fibrinogen standard with matches at 6 of the peaks; 1725, 1647, 1530, 1454, 1312 and 955cm-1 (Table 1).

Conclusion(s): Following elimination of the sodium citrate additive impact there remained close alignment of the citrated plasma PCA loading marker bands with the measured fibrinogen. This demonstrates that ATR-FTIR has the potential to analyse coagulation parameters such as fibrinogen and could be developed into a rapid point of care test.