Commentary: Psoriasis treat to target: defining outcomes in psoriasis

COMMENTARY

In moderate to severe psoriasis, there has been a long-lasting tradition to define outcome as a relative change from baseline PASI, with the classical PASI 75 being more recently replaced by PASI 90 or 100. However, this concept is dated, mainly due to the impressive development of anti-interleukin therapies and an increasing interest in real-world evidence. One underlying problem is that a relative PASI change might reflect more the point of departure than the current treatment under evaluation. It is therefore important that we look at alternatives.

Several studies have pointed out that we still have an unacceptably large proportion of psoriasis patients severely under-treated. The definition of absolute rather than relative treatment targets is an important tool, as these targets can be easily applied in everyday clinical practice. The classic approach is to define an absolute treatment target through an expert panel. In contrast, Mahil et al. took an innovative approach by employing real-world evidence data from the UK BADBIR. They calculated that absolute PASI ≤ 2 was concordant with PASI 90 in 90% of cases and found PASI ≤ 2 to be an adequate treatment target. Likewise, PGA clear/almost clear was suggested as an alternative, based on strong correlations between PASI and PGA scores. This article is therefore an important contribution towards establishing applicable treatment goals.

Another question is which dimension of psoriasis should be our target. I think we should be ambitious, aiming not just for clear skin but also include quality of life and optimal health in its broadest sense.

A quarter-century of experience with the DLQI has shown its value as an additional measure which compensates for the limitation of the PASI which judges body surface, not impact on life. Two persons with the same PASI can experience the impact of psoriasis on their quality of life quite differently. Also, the same person over the course of a lifetime, can change how she perceives the impact of her skin symptoms on her quality life.

We should direct the current discussion of therapy targets towards broader contemporary treatment targets. In Sweden, we have been monitoring outcomes in the national psoriasis register for 14 years in three dimensions, PASI, DLQI and the generic quality of life measurement EQ-5D. This reflects that psoriasis is a systemic disease comprising skin involvement alongside somatic and psychiatric comorbidities. Furthermore, caregiver and patient alike are reminded about the interdependency of these factors when they look at outcomes longitudinally. Such an approach even facilitates the implementation and evaluation of non-pharmaceutical interventions, as lifestyle changes will affect the patient more broadly as reflected by PASI or PGA alone.

Contemporary medicine should be practiced in a way where the patient’s experience of the disease is evaluated alongside clinical measurements. We have to implement treatment targets deeper than skin that facilitates the dialogue between caregiver and patient. This is of particular importance now as the COVID-19 pandemic clarifies the vital importance of general health and fitness as well as the trust between caregiver and patient.