OBJECTIVE: To investigate the intrinsic fluorescence spectrum of gastric juice as a diagnostic method for gastric cancer. METHODS: We collected gastric juice by gastroscopy in 1,870 patients from May 2001 to March 2006, of whom 202 were involved in a preliminary test, 162 in experimental optimization and 1,506 in clinical verification. The best dilution and pH value were chosen in the experimental optimization phase. Clinical verification was based on optimized samples. Intrinsic fluorescence spectra were measured in all samples with a fluorescence spectrophotometer using an excitation wavelength of 288 nm. RESULTS: The first peak of fluorescence intensity (P(1) FI) of the intrinsic fluorescence spectrum was significantly higher in gastric juice from patients with gastric cancer than from those with benign lesions. There was no significant difference in the P(1) FI differences between patients with benign and malignant lesions with samples diluted by 20-fold to 80-fold and from pH 9 to pH 11. Clinical verification in 1,506 patients showed that P(1) FI >/= 76.5 was the optimal cut-off on the receiver operating characteristic curve for diagnosing gastric cancers: sensitivity was 83.2%, specificity 80.7% and accuracy 82.0%. CONCLUSIONS: P(1) FI of the intrinsic fluorescence at 288 nm is significantly higher in patients with gastric cancers than in individuals with benign lesions. As a clinical indicator of gastric cancer, its sensitivity, specificity and accuracy were high.
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