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