Probing the use of fluorescence spectroscopy as a novel diagnostic tool in patients with rheumatoid arthritis: Applicability in the detection of secondary amyloidosis

BACKGROUND Secondary amyloidosis is a frequently reported complication of rheumatoid arthritis. Currently, accepted diagnostic protocols for secondary amyloidosis involve histopathological and histochemical examinations of collected tissue specimens. The purpose of the current report was to evaluate the value of fluorescence spectroscopy as a supplementary tool in the diagnosis of secondary amyloidosis. MATERIAL/METHODS Tissue specimens were collected from abdominal folds, gingiva or rectal mucosa of 99 patients affected with rheumatoid arthritis. Tissue samples were subjected to preliminary clinical observations, histopathological examinations and laboratory tests. These procedures were used to subdivide tissue samples into either amyloid-containing or amyloid-free control subgroups. All collected tissue samples were examined with the use of a designated spectrofluorometer and fluorescence spectral images were generated. RESULTS It was found that fluorescence spectra for amyloid-containing tissues were typically characterized by a double emittance peak. In contrast, amyloid-free samples were characterized by fluorescence spectra with a single λmax value. Specimen collection site, age and sex did not appear to influence the morphology of electromagnetic spectra, which were generated for both amyloid-containing and amyloid-free tissue samples. The sensitivity of the fluorometric approach was ~78% and the specificity was 100%. Possible shortcomings of the technique may be due to the limit of detection of the instrument used. CONCLUSIONS Fluorescence spectroscopy may potentially be used as an effective, instantaneous and low-cost diagnostic tool for suspected secondary amyloidosis in patients affected with rheumatoid arthritis.