Multimodal Diagnosis of Pityriasis Versicolor: Clinical, Wood’s Lamp, Dermoscopic and Microbiological Features

Abstract

Objective: To evaluate the accuracy of diagnosing Pityriasis versicolor using clinical, woods lamp dermoscopic & microbiological features. Material and Methods: A prospective study (lasting one year) was conducted at the Dermatology, Venereology and Leprology (DVL) OPD of a rural tertiary health centre. The number of clinically suspected cases of Pityriasis versicolor (PV) was 50. Inclusion criteria included patients with scaly macules on the trunk or neck or arms. A standard clinical examination, Wood lamp examination (365 nm in a dark room) and polarized and non-polarized dermoscopy, 10% potassium hydroxide (KOH) microscopy, fungal culture on Sabouraud Dextrose Agar (SDA) and lipid-enriched Dixon agar was performed. Analysis was done using descriptive statistics, Chi-square/Fishers exact tests and diagnostic accuracy (sensitivity, specificity, positive predictive value, negative predictive value). The significance value of 0.05 was taken to be significant. Results: 68.0% of 50 patients had hypopigmented lesions. Clinical examination was 77.3 and 66.7 sensitive and specific respectively. The sensitivity of the lamp used by Wood was 81.8% and the fluorescence was yellow-gold. Dermoscopy proved to be 86.4% sensitive with loss of pseudo-network patterns, fine white scales and accentuation of perifollicles. It was cultured on only a 24.0% of the occasions (12/50) with the most common isolates being M. globosa (50) and M. furfur (33.3). KOH microscopy demonstrated a much higher detectability (80.0%) as compared to culture. The combination of multimodal (clinical + Woods lamp + dermoscopy + KOH) increased the diagnostic accuracy to 96.0% (p<0.001 over single methods). Conclusion: Multimodal method has a significant positive effect on the diagnostic accuracy of PV. Considering the low culture percentage of fungal culture in the Malassezia in routine environments, KOH microscopy is the primary microbiological test, and dermoscopy is an extremely helpful non-invasive complement. The lamp of wood aids in differentiating between PV and other pigmentary lesions. We propose a diagnostic algorithm that is stepwise and focused on accessible modalities that are point-of-care.