Fourier transform infrared (FTIR) spectroscopy is a vibration spectroscopy that uses infrared radiation to vibrate to absorb the molecular bonds in its absorbed sample. The main purpose of this study was to evaluate FTIR spectroscopy as a novel diagnostic tool for lymph node metastasis (LNM) of gastric cancer. We collected 160 fresh non-metastatic and metastatic lymph nodes (80 each) from 60 patients with gastric cancer for spectral analysis. FTIR spectra of lymph node (LN) samples were obtained in the wavenumber range of 4000 cm-1 to 900 cm-1. We calculated the changes in the ratio of spectral intensity (/ I1460). Principal component analysis (PCA) and Fisher's discriminant analysis (FDA) were used to distinguish malignant from normal LN. Four significant bands at 1080 cm-1, 1640 cm-1, 1740 cm-1 and 3260 cm-1 separated metastatic and non-metastatic LN spectra into two distinct groups by PCA.T-tests showed that, along with the relative intensity ratios (I1080/I1460, I1640/I1460, I3260/I1460, I1740/I1460), these band ratios were also able to differentiate between malignant and benign LN spectra. Six parameters (P1080 cm-1, P1300 cm-1, I1080/I1460, I1640/I1460, I3260/I1460, I1740/I1460) were selected as independent factors to set up discriminant functions. The sensitivity of FTIR spectroscopy in diagnosing LNM was 95 % by discriminant analysis. Our study suggested that FTIR spectroscopy can be a useful tool to examine LNM with high sensitivity and specificity for LNM diagnosis. Therefore it can be used in clinical practice as a non-invasive method.
Keywords: Fisher’s discriminant analysis; Fourier transform infrared spectroscopy; Gastric cancer; Lymph nodes; Principal component analysis.
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