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29-12-2011 | Immunology | Article

New classification system for grading common nail disease effective

Abstract

Free abstract

MedWire News: Researchers have developed a new numeric system for defining the severity of onychomycosis, a common disease of the nail caused by molds and yeasts, based on a number of disease characteristics.

"Although many reports describe factors that predict a poor response to treatment, there is currently no system to clinically grade the severity of onychomycotic nail disease," say Boni Elewski (University of Alabama at Birmingham, USA) and colleagues.

They add: "Such a scale is necessary for clinical trial inclusion criteria, for clinician guidance in treatment choice, and for the prediction of therapeutic outcome."

The Onychomycosis Severity Index (OSI) was developed by a group of five dermatologists specializing in nail disorders and onychomycosis, one dermatology resident with an interest in nail disorders, and a statistician.

Clinical features chosen for OSI scoring were area of involvement, proximity of disease to the nail bed, occurrence of fungi, and presence of severe nail psoriasis larger than 2 mm.

The OSI score was determined by multiplying the score for the area of involvement (range 0-5) by the score for the proximity of disease to the nail bed (range 1-5). Ten points were added for the presence of fungi or for nail psoriasis affecting more than 2 mm.

Mild, moderate, and severe onychomycosis corresponded with scores of 1-5, 6-15, and 16-35, respectively.

For the first assessment of the OSI system, 37 dermatologists scored eight photographs of onychomycosis after being given training on the new scale.

A high test reliability was obtained, with only 15 errors observed among the 136 analyzed photographs. All errors were related to misidentification of nail fungi.

For the second assessment, three dermatologists, including an expert in use of the OSI, evaluated 49 nails from patients with onychomycosis. Again, the scoring system showed very high levels of reliability.

"The OSI is a new, simple, objective, and reproducible numeric system to grade the severity of onychomycosis," conclude the authors in the Archives of Dermatology.

By Ingrid Grasmo

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