Comparison of visual assessments versus planimetry assessments in a large-scale clinical trial of onychomycosis.

Computerized nail planimetry is an objective means of accurately assessing affected nail areas, versus the standard visual estimation method. However, no published comparison of visual assessment with planimetry is currently available on onychomycosis to support this recommendation. This article evaluates efficacy based on visual assessment compared to planimetry measures during the course of an 84-week large-scale, single-site trial of subungual dermatophyte onychomycosis, to determine the validity of planimetry versus visual assessment. Visually assessed percentage of affected area of the target toenail was compared with planimetry calculated measurements made from digital photographs. Comparison showed good statistical agreement of visual and planimetry measures based on correlation coefficient. Visual and planimetry assessments at week 84 were within 10% of each other in 92% of cases, and within 5% of each other in 74% of comparisons. However, errors in visual assessment artificially inflated the cure rates by 9% and 11% at weeks 84 and 48, respectively. Furthermore, the significant difference in effective cure between regimens using visual methods loses significance when planimetry measures are used. The results suggest that objective measures such as planimetry will reduce the impact of visual assessment errors, and techniques to increase the standardization of onychomycosis assessment are warranted.