Dermoscopy and Wood’s Lamp Compared with Potassium Hydroxide Microscopy in Pityriasis Versicolor: A Cross-Sectional Diagnostic Accuracy
Abstract
Background: Pityriasis versicolor is a common superficial fungal infection caused by Malassezia species. Diagnosis is often clinical, with confirmation through potassium hydroxide microscopy or Wood’s lamp examination. Dermoscopy has emerged as a non-invasive diagnostic tool, yet evidence from Sub-Saharan Africa remains limited.
Objective: To evaluate the diagnostic performance of dermoscopy compared with Wood’s lamp, using potassium hydroxide microscopy as the reference standard.
Methods: A hospital-based cross-sectional study was conducted among 113 adult patients with clinically diagnosed pityriasis versicolor at a tertiary dermatology clinic in South-East Nigeria. All participants underwent Wood’s lamp examination, dermoscopic assessment, and potassium hydroxide microscopy. Sensitivity, specificity, positive predictive value, negative predictive value, and receiver operating characteristic analysis were calculated.
Results: Potassium hydroxide microscopy confirmed pityriasis versicolor in 62 of 113 participants (54.9%). Dermoscopy demonstrated 100% sensitivity and 100% negative predictive value, with specificity of 7.8% and positive predictive value of 56.9%. Wood’s lamp showed sensitivity of 80.6%, specificity of 66.7%, positive predictive value of 74.6%, and negative predictive value of 66.7%. Receiver operating characteristic analysis revealed an area under the curve of 0.539 for dermoscopy and 0.737 for Wood’s lamp.
Conclusion: Dermoscopy identified all potassium hydroxide-positive cases in this cohort and may serve as a useful screening tool in low-resource settings. Wood’s lamp demonstrated higher specificity. Integrating dermoscopy with clinical assessment may enhance early diagnosis where microscopy is unavailable.
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