Clinical data on diffuse reflectance and autofluorescence spectra of leprosy affected skin

A systematic study of the diffuse reflectance and autofluorescence spectra of leprosy-affected skin was performed. Forty-six patients with five subtypes of leprosy – tuberculoid leprosy (TT), borderline tuberculoid (BT), mid-orderline (BB), borderline lepromatous (BL), and lepromatous leprosy (LL) – were examined. The measurement setup comprised a spectrometer attached to one leg of Y-shaped optical fiber cable and a broadband halogen light source (HAL, for diffuse reflectance measurements) or a narrowband light-emitting diode with a band-center wavelength of 385 nm (LED, for autofluorescence measurements) attached to the other leg of this cable. During the measurements, the joint end of the cable was attached to the patient lesion site and outside it, to the healthy skin. Spectral features of all lesional spectra and the residual (lesion-healthy) spectra were analysed.

The first results showed a potential of residual diffuse reflectance for leprosy differentiation in the wavelength range 600–686 nm, with prominent peaks at 623 and 666 nm. Residual autofluorescence indicated potentially highest sensitivity in the 474–523 nm spectral range.

The noise and statistical dispersion of currently available data were too large to draw final conclusions on the clinical applicability of a spectroscopy-based leprosy diagnostic test; more representative spectral data on leprosy-specific changes are required.