Comparison of Two Specimen-Collection and Microscopy Methods for the Rapid Laboratory Diagnosis of Seborrheic Dermatitis- A Pilot Study

ABSTRACT

Malassezia spp. causes seborrheic dermatitis. For laboratory diagnosis, skin scrapings are collected and mounted in potassium hydroxide (KOH) for microscopy and processed for culture. Obtaining scrapings has disadvantages and KOH lacks colour contrast making interpretation difficult. This pilot study compared the results of specimen collection by cellophane tape method with scraping method. It also compared microscopy using Chicago Sky Blue 6B (CSB) stain plus KOH with the conventional method using KOH alone.METHODSSkin specimens were collected from the affected sites of 80 patients by scraping and cellophane tape. Specimens were subjected to KOH examination, KOH plus CSB stain, and culture for the presence of Malassezia spp.RESULTSA total of 160 specimens were collected from 80 patients for microscopy. Of 160 specimens, each was subjected to KOH and CSB plus KOH, 145 (91%) demonstrated Malassezia spp. by CSB plus KOH and 124 (77.5%) by KOH alone (p= 0.001). Cellophane tape method yielded 141 (88%) positive results compared to 128 (80%) by skin scraping (p=0.047). The odds of detecting Malassezia spp. was 4.4 times greater when the specimen was collected by cellophane tape and subjected to microscopy with CSB and KOH than when it was collected by scraping and examined microscopically with KOH alone (p= 0.002).CONCLUSIONSCellophane tape is a convenient method for specimen collection. CSB stain provides colour contrast and enables easy identification of fungal elements.