Administrative data and scientific evidence: a lesson from France - the safety of systemic treatment for psoriasis during the COVID-19 pandemic.

Concerns have repeatedly been raised about the safety of systemic treatment for immune‐related conditions during the COVID‐19 pandemic. Regarding psoriasis, reassuring data on the risk of hospitalization and mortality due to SARS‐CoV‐2 infection have so far been provided for patients on systemic treatment, , , with some papers even suggesting a protective effect of biological treatment for the most ominous outcomes. As a matter of fact, most of the available studies were published under the pressure to provide some kind of evidence, and were either underpowered or suffered from important methodological flaws, such as the lack of appropriate denominators, making their estimates questionable. , There is a need to develop reliable monitoring systems on a large scale at sustainable costs.

In this issue of the BJD, Penso et al. present the results of a large retrospective nationwide cohort of patients with psoriasis in France. The study was based on the French national health data system, which covers the entire French population, and linked two different sources of administrative data: the National Health Insurance Claim Database and the National Hospital and Discharge Database.

The study, which relied on the data of more than 1 million patients with psoriasis, was carefully designed with several covariates controlled for. Notably, it included a deprivation index, as socioeconomic factors are a major determinant of all‐cause mortality and COVID‐19 mortality. The first and second waves of the COVID‐19 pandemic were analysed separately, as modifications in medical care and risk‐mitigating behaviour may have occurred during the two periods.

In the analysis, systemic treatments for psoriasis, including both conventional therapies and biologics, were not associated with an increased risk of in‐hospital mortality due to COVID‐19, although an increased risk of hospitalization was found for patients receiving conventional systemic treatment in both waves of the pandemic, and during the second wave for patients under biologics. Such differences in estimates may be attributed to changes in risk‐mitigating behaviour by patients on biologics during the two phases of the pandemic. Comorbidities, irrespective of the treatment received, may also affect risk estimate, as documented by the increased risk of hospitalization for patients on topical treatment only. Such an increased risk disappeared when considering the subgroup of patients without comorbidities. Despite some previous suggestions, there was no prophylactic impact of long‐term biologics use on the risk of in‐hospital death from COVID‐19. A rather surprising figure was the low number of patients with psoriasis receiving any treatment for their disease: more than two‐thirds of all patients did not receive any medication during the two pandemic waves, and only about 6% of all the patients were on a systemic treatment. If these figures reflect reality, then studies restricted to hospital patients should be considered with great caution.

There is now enough evidence to justify the continuation of routine psoriasis care during the COVID‐19 pandemic, while stopping systemic treatment in the absence of infection is not advisable.

The French group should be commended on their excellent study, which shows how administrative data can be used efficiently, effectively and creatively to produce robust evidence when considering risk assessment at the population level.

Author Contribution

Simone Cazzaniga: Conceptualization (equal); Writing‐original draft (equal). Luigi Naldi: Supervision (equal); Writing‐original draft (equal).