No abstract

Sir, We read with interest the article by Charman et al. 1 and agree in part with their conclusion that measurements of body surface area are unreliable as discrete numbers. We have previously described the Dermatology Index of Disease Severity, 2 which is a rapid and simple assessment of skin disease with high interobserver reliability. When we were developing this index, we experienced frustration similar to that of Charman et al. when using discrete measurements of body surface area of active disease. We found, however, that there was good to excellent concordance (k = 0´76) when the observers were asked to rate within the following ranges: 0±5%, 6±19%, 20±90% and . 90%. The disagreements were then limited to the boundaries of each range and were therefore minimized. These boundaries were chosen to reflect the most likely therapeutic and monitoring decision points in clinical practice.We also agree that functional limitations are important to assess, e.g. involvement of hands and feet, which can severely limit activities. We incorporated this assessment into our staging system, basing the presence of functional limitation on a simple performance measurement assessed by the observer and not on the history as provided by the patient. We found the history to be variable depending both upon the patient and on the persistence and specific questions of the observer. We chose not to measure symptoms such as pain, itching or cosmetic disfigurement because these have not been standardized. At present, we recommend that these parameters be assessed by other instruments that can be independently tested and verified.