Wood’s Lamp in Differential Diagnosis of Tinea Versicolor, Tinea Capitis, and Erythrasma: a Comparative Study of Ultraviolet Light and Blacklight Blue Lamp

Abstract

In humid tropical climes, particularly in southern Thailand, fungal dermatitis is a major problem. Tinea capitis, which is an infection caused by Microsporum canis, with laboratiry investigation it is characterized by a blue-green pteridine glow which is different from tinea versicolor caused by Malassezia furfur, it shows a golden yellow light, and erythrasma infection caused by a bacteria - Corynebacterium minutissimum, has a coral red glow. The Wood’s lamp equipment in the Southern Regional Hospital of Tropical Dermatology has been in use for over 20 years; and has an average of 126 service users a year. After the equipment degrades, there is an impact on the waiting time. To improve the services, an alternative spare part has to be explored. The purpose of this study was to compare the sensitivity, specificity, and accuracy of the Wood’s lamp with the ultraviolet light lamp and the Blacklight blue lamp in the differential diagnosis of tinea versicolor, tinea capitis, and erythrasma. It was conducted during 2019–2020 with 81 volunteers, and a data collection form was used to collect variables on the diagnosis of skin diseases, laboratory findings by employing Wood’s lamp, ultraviolet light, and Blacklight blue lamp; and followed by KOH preparation examination and reported fungal species. The sensitivity, specificity, and accuracy of the data were then evaluated using diagnostic test statistics. KOH preparation was used as the reference procedure for diagnostic comparison. According to the findings, the analytical techniques’ sensitivity, specificity, and accuracy were 82.05%, 97.62%, and 90.12% for the diagnosis with both Wood’s lamp ultraviolet light and Blacklight blue lamp, respectively, which did not show significant difference. Thus, the Blacklight blue machine was innovated to become an diagnostic tool which could lower the cost of purchase by 5,000 baht as compared to 20,000 baht for Wood’s lamp machine. The new equipment could also be utilized in combination with cameraFi applications by entering the findings into the hospital’s computer system to enable precise and correct treatment.