Disease severity is assessed by a visual assessment of the number of lesions and extent of disease. Although numerous visual assessment methods of varying complexity exist, at the basic level they can be subdivided into grades or counts. In both cases, there are three levels at which assessment can be made:
1. an overall or 'global' evaluation
2. subdivision according to the predominant morphological component (i.e. inflammatory or non-inflammatory)
3. separate evaluations of each individual lesion type, for example comedones, papules and pustules.
Results are generally expressed as an absolute or percentage change from onset of therapy and are commonly transformed to give the numbers of individuals attaining a given level of improvement, for example 50%.
Other important outcomes for the evaluation of therapy are changes in quality of life, scarring, patient satisfaction, tolerability and adverse events, speed of action and treatment-free interval.
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