INTRODUCTION
The significant reduction in quality of life and psychosocial disability suffered by psoriasis patients highlight the need for prompt, effective, and long-term disease control. The time taken for psoriasis patients to achieve a clinically relevant improvement in their disease is an important aspect of patient management and education, especially in very acute or severe forms,1 and has been shown to be very important to psoriasis patients.2 Along with efficacy, rapid disease improvement has been rated as the most important treatment goal by almost 95% of patients with moderate-to-severe psoriasis.3 The advent of biologic therapies has provided greatly improved treatment outcomes. However, data on how quickly these treatments become effective are sparse. We aim to review the current literature to determine the time needed for specific biologic treatments to achieve a given treatment goal, and discuss some of the limitations that exist within the data.
Limitations in Approach
Onset of action has not been a primary or secondary endpoint in any clinical trial. Calculations have been derived from linear interpolation between different time points or Kaplan-Meier approximations, whereby predicted mean or median times often lie between two study visits limiting the precision of any estimate. With some biologics, data are available from more than one study and onset of action has been calculated as a weighted mean taking into account the number of patients in the individual studies.4 However, it is not possible to remove bias that may have arisen due to different study quality because of their limited numbers. Different body regions may provide differing responses, with the head/neck and trunk being shown to respond quicker than psoriasis of the arms and legs;5,6 and both ethnic and regional differences have been reported.7,8 In addition, some important data were not publicly available to fully appreciate the impact of any concomitant medication, washout phases, or baseline disease severity. For example, a very high initial Psoriasis Area and Severity Index (PASI) may allow for a more significant and faster reduction in severity over the first few weeks. Where baseline PASI data are available these are indicated in our review.
Determining Onset of Action
A large number of clinical measures of psoriasis (in excess of 50) are used in clinical trials and daily practice.9 The PASI is the most commonly used clinical measure in research, evaluating
