Measurement of body surface area involvement in atopic eczema: an impossible task?

Estimation of the area of skin involvement is an important part of atopic eczema severity scoring systems. We examine the variation seen when six dermatologically trained observers assessed disease extent in six patients with atopic eczema using the rule of nines. The median scores ranged from 4.8% to 37.2%. The level of agreement for the classification of scores into quintile categories was 55%, with a chance-corrected agreement (kappa statistic) of 0.09, representing very poor interobserver agreement. To measure the effects of health care intervention accurately, reliable methods of assessment should be used. Scoring methods in which reliability cannot be demonstrated may be misleading and should be interpreted with caution.