Toenail assessment tool for quantitation of visibly infected mycotic nail plate in onychomycosis.

Typically, the amount of mycotic nail involvement in onychomycosis (fungal infection of the nail) before and after drug therapy is determined visually. Because there is an inherent element of subjectivity, it is difficult to accurately measure and compare results across clinical trials or to assess how much improvement has been achieved in response to therapy. We developed a simple tool for measuring mycotic nail involvement. This novel tool consists of a large grid containing 5 toenail templates of varying nail morphologies that are derived from the actual shape of the toenail of the great toe in several males and females, and one standardized computer-generated nail shape. The toenail templates are presented in 7 different sizes to match different nail sizes. Each toenail template is further divided into 8 segments, each comprising approximately 12.5% of the total nail surface. Measurement of the percentage of mycotic nail involvement is accomplished by the following procedure: (1) placing tracing film over the target toenail; (2) tracing the outline of the entire toenail, followed by tracing the affected portion of the toenail on the same film; (3) placing the tracing film over a nail template on the grid that best fits the shape of the toenail; and (4) counting the number of grid segments that correspond to 50% or more involvement. To assess feasibility, the tool was used in a large randomized trial involving over 30 sites and 500 subjects with onychomycosis. This tool is a more accurate and less biased alternative to visual assessment for measuring nail involvement or progression of nail clearing.