Inter-observer reliability of the Onychomycosis Severity Index depending on clinical experience: A review of 50 cases.

Background: Onychomycosis (ONM) is the most prevalent nail unit pathology, and its severity and monitoring are often based on the visual judgement of clinicians.

Objective: The objective of this study is to assess the reliability of the Onychomycosis Severity Index (OSI) classification when utilized by three clinicians with varying levels of clinical experience: an experienced podiatrist (with 5 years of experience), a moderately experienced podiatrist (with 2 years of experience) and an inexperienced podiatrist (a recent graduate familiar with the OSI classification but lacking clinical experience). Additionally, we compared the severity assessments made through visual inspection with those determined using the OSI by different clinicians.

Methods: We evaluated reliability using the intraclass correlation index (ICC), analysing 50 images of ONM.

Results: The OSI demonstrated a very high level of reliability (ICC: 0.889) across clinicians, irrespective of their experience levels. Conversely, a statistically significant increase in severity was observed when comparing visual assessments with the OSI (p < .001) for ONM severity evaluation.

Conclusion: The OSI proves to be a reproducible classification system, regardless of the clinical experience of the practitioner employing it.