title: Fluorescence spectroscopy as a tool to in vivo discrimination of distinctive skin disorders.
abstract: BACKGROUND
  Fast and non-invasive analytical methods, as in fluorescence spectroscopy, have potential applications to detect modifications of biochemical and morphologic properties of malignant tissues. In this study, we propose to analyze the fluorescence spectra using k-Nearest Neighbours algorithm (k-NN) and ratio of the fluorescence intensity (FI) to differentiate skin disorders of distinctive etiologies and morphologies.
  
  
  METHODS
  Laser-induced autofluorescence spectra upon excitation at 408nm were collected from basal cell carcinoma (BCC) subtypes (n=45/212 spectra), psoriasis (PS) (n=37/193 spectra) and Bowen's disease (BD) (n=04/19 spectra) lesions and respective normal skin at sun-exposed (EXP) and non-exposed (NEXP) sites of the same patient.
  
  
  RESULTS
  The mean ratios of FI values at selected wavelengths of emission (FI600nm/FI500nm) were significantly lower in BCC and PS lesions compared to EXP [P=0.0001; P=0.0002, respectively]; but there were no significant differences between abnormal conditions. The analysis of fluorescence spectra using k-NN can discriminate normal or abnormal skin conditions (EXP, BCC, BD, PS) of distinctive etiology, neoplastic or inflammatory (BCC, BD and PS) and morphologies (nodular and superficial BCC, BD and PS) as high as 88% and 93% sensitivity and specificity means, respectively; also, similar erythematous-squamous features (superficial BCC, BD and PS) with 98% and 97% sensitivity and specificity means, respectively. The k-NN computational analysis appears to be a promising approach to distinguish skin disorders.
authors.affiliation: Institute of Physics of São Carlos, University of São Paulo, Av. Trabalhador São-Carlense, 400 - Parque Arnold Schimidt, São Carlos, SP, 13566-590, Brazil; Medical School of Ribeirão Preto, University of São Paulo, Av. Bandeirantes, 3900 - Monte Alegre, Ribeirão Preto, SP, 14048-900, Brazil.
authors.forename: Vitoria Helena
authors.initials: VH
authors.lastname: Maciel
authors.affiliation: Institute of Physics of São Carlos, University of São Paulo, Av. Trabalhador São-Carlense, 400 - Parque Arnold Schimidt, São Carlos, SP, 13566-590, Brazil.
authors.forename: Wagner Rafael
authors.initials: WR
authors.lastname: Correr
authors.affiliation: Institute of Physics of São Carlos, University of São Paulo, Av. Trabalhador São-Carlense, 400 - Parque Arnold Schimidt, São Carlos, SP, 13566-590, Brazil.
authors.forename: Cristina
authors.initials: C
authors.lastname: Kurachi
authors.affiliation: Institute of Physics of São Carlos, University of São Paulo, Av. Trabalhador São-Carlense, 400 - Parque Arnold Schimidt, São Carlos, SP, 13566-590, Brazil.
authors.forename: Vanderlei Salvador
authors.initials: VS
authors.lastname: Bagnato
authors.affiliation: Medical School of Ribeirão Preto, University of São Paulo, Av. Bandeirantes, 3900 - Monte Alegre, Ribeirão Preto, SP, 14048-900, Brazil. Electronic address: cssouza@fmrp.usp.br.
authors.forename: Cacilda
authors.initials: C
authors.lastname: da Silva Souza
mesh_terms: D001913:Bowen's Disease / Q000175:diagnosis / Q000473:pathology; D002280:Basal Cell Carcinoma / Q000175:diagnosis / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis / Q000473:pathology; D006801:Humans; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D011565:Psoriasis / Q000175:diagnosis; D012680:Sensitivity and Specificity; D012871:Skin Diseases / Q000175:diagnosis* / Q000473:pathology*; D012878:Skin Neoplasms / Q000175:diagnosis / Q000473:pathology; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D017319:Photosensitizing Agents
keywords: Basal cell carcinoma; Bowen’s disease; Fluorescence spectroscopy; Psoriasis