Objective determination of skin phototypes in healthy children by diffuse reflectance spectroscopy.

INTRODUCTION: The clinical method of evaluating the color of the skin based on visual assessment is subjective and thus inaccurate. The objective determination of skin phototypes and levels of melanin in the skin is important for diagnosing the pigment disorders and also for adequate photoprotection. Diffuse reflectance spectroscopy (DRS) is a non-invasive, precise and objective method for quantifying the melanin levels. OBJECTIVE: The aim of this study is to assess the characteristic DRS spectrum of healthy skin in children and to detect the differences between them based on age, gender and skin phototype. MATERIAL AND METHODS: Skin pigmentation was measured by DRS in 73 children patients with experimental spectrophotometer UM-ES600. The amount of melanin is quantified from the obtained DRS spectra by proposed melanin quantification angle α obtained by comparing the reflectance properties of skin sample and universal depigmented sample (albino skin). RESULTS: We evaluated spectroscopic characteristics of children's healthy skin depending on age, gender and phototype. The value of melanin quantification angle α grew proportionally from phototype I to phototype IV, without any correlation to age or gender. We confirmed a clear association between clinical determination of Fitzpatrick's skin phototypes and objective data collected by DRS and related angle α. CONCLUSIONS: Our proposed index quantifies the difference in melanin levels in healthy children skin and also for different skin phototypes. The proposed method and melanin quantification angle α can further be used for the objectification of the progress of pigmentary diseases or for monitoring the effect of their therapy (Tab. 5, Fig. 4, Ref. 29).

An objective assessment of melanin in vitiligo skin treated with Balneo PUVA therapy.

BACKGROUND: Visual clinical methods of skin color evaluation for diagnostic purposes are so far mostly subjective and thus inaccurate. We present a modified method of melanin amount measurement based on diffuse reflectance spectroscopy (DRS). This method is non-invasive and objective, and allows easy quantification and comparison of melanin levels. MATERIAL AND METHODS: Skin pigmentation was measured by DRS method in 0-18 year old patients at the Department of Pediatric Dermatovenerology, School of Medicine Comenius University Bratislava. Patients were treated for their vitiligo by Balneo PUVA treatment twice weekly. Each patient had measured his remittance spectra from the treated vitiliginous skin before the treatment was started, after 10 irradiations of Balneo PUVA and at the end of the treatment after 25 irradiations of Balneo PUVA. In our study as a reference skin for spectroscopic assessment of melanin in vivo was used the averaged remittance spectra (measured on the inner arm) from the sample of 10 albino patients. The remittance spectra obtained from the vitiligo patients were ratioed against the newly described remittance reference albino skin. We exploited the linear behavior of the spectral curve in the 620-720 nm interval (significant for melanin absorption) and used the slope of the regression line to compute the quantification index α. RESULTS: By clinical examination before the Balneo PUVA therapy, after the 10th dose of Balneo PUVA therapy as well as at the end of the complete course of Balneo PUVA therapy (after 25 irradiations) we recorded a marked increase of pigmentation in all treated patients for their vitiligo. In each patient the values of melanin quantification angle α were calculated. Statistically we found a significant difference between the melanin quantification angle α in vitiliginous skin before, during the 10th dose of treatment and after the treatment. Similar significant difference was also observed between treated and non-involved skin. We could confirm a clear association between clinical visual examination of treated vitiligo lesions, objective data collected by DRS and melanin quantification angle α. CONCLUSIONS: By using a new standard for the reference skin (albino skin) we could more exactly compare melanin levels in different subjects. Our proposed melanin quantification angle α expresses the extent of the difference in melanin levels between the examined skin lesions. We successfully used this index to quantify the variations of melanin (progress of repigmentation) throughout different stages of treatment of the same lesion and also to objectively evaluate the final effect of the therapy. In the present study, we showed that the diffuse reflectance spectroscopy (DRS) may be suitable method to measure skin colour and the content of human skin melanin in vivo.