Diagnosing Oral Candidiasis using Autofluorescence Microscopy

Objectives: This study aimed to investigate the diagnostic accuracy of the Pap staining method & of autofluorescence microscopy (AF) in the detection of subclinical oral candidiasis. Methods: Oral mucosal specimens were sampled from patients presenting at the dental clinics of the University of the Western Cape, in Cape Town, South Africa (n=80). The dorsal tongue, buccal mucosae, and labial vestibulae were sampled using brush cytology. Two parallel exfoliative smears were prepared from each brushing sample. Each slide pair was stained, one with Periodic Acid-Schiff (PAS) and the corresponding slide with Papanicolaou (Pap) stain. Phase 1: The slides were then screened by medical cytologists of the NHLS at Tygerberg Hospital. These baseline screening results formed the control group for this study. Phase 2: The Pap stained slides were screened for Candida with light microscopy by observer A, and then observer B. Phase 3: The slides were renumbered and viewed under AF microscopy by the observers. Results were then correlated against the control group to determine sensitivity, specificity, and diagnostic accuracy. Results: Pap stained exfoliated oral squamous cells and oral microflora autofluoresce under LED UV light. Candidal hyphae contrast distinctly bright green in colour. Pap stained hyphae appear purple-pink under normal light microscopy. Phase 2 results (Pap and normal light microscopy) indicated a sensitivity of 61.8% and 75.7% for observers A and B; specificity of 72.3% and 78.7%. Phase 3 results (AF microscopy) indicate a sensitivity of 39.4% and specificity of 83% for observer A. Sensitivity and specificity for observer B were 30.3% and 95.7%. Conclusions: Pap staining with AF microscopy alone is not sufficiently effective / reliable on its own when screening for oral candidiasis. PAS staining with normal light microscopy currently remains the gold standard. AF is a good ancillary test when screening Pap stained smears for fungal pathogens.