Why Psoriasis Experts Are Rethinking TB Testing for IL-17, IL-23 Inhibitors

Routine tuberculosis (TB) screening before starting a biologic has been standard practice in psoriasis care for decades. A new joint position statement from the National Psoriasis Foundation (NPF) and the International Psoriasis Council (IPC) questions whether that requirement should still apply to interleukin (IL)-17 and IL-23 inhibitors.

In the first segment of this HCPLive Special Report, 2 co-authors of the statement discussed how the field arrived at its current approach. They were Andrew Blauvelt, MD, MBA, adjunct professor in the Department of Dermatology at the University of Maryland School of Medicine and owner of Blauvelt Consulting, LLC, and Joseph F. Merola, MD, MMSc, chair of the Department of Dermatology at UT Southwestern Medical Center.

Where Did TB Testing Requirements for Psoriasis Biologics Come From?

Blauvelt explained that the group reviewed the available evidence on TB risk with IL-17 and IL-23 inhibition and reached a position that challenges conventional thinking. Testing requirements for all biologics in psoriasis trace largely to the tumor necrosis factor (TNF) inhibitor era. TNF blockers are known to reactivate latent TB, a risk supported by both a biologic rationale and clinical data. For the 2 newer classes, however, he said no such evidence has emerged to date.

Merola credited Blauvelt with leading the effort. He described the statement as a major departure from a practice clinicians have followed almost reflexively for years. He noted that testing for IL-17 and IL-23 inhibitors was carried over from TNF inhibitors and other granuloma-disrupting therapies. It was not based on direct clinical evidence of risk or on how the drugs work.

What Does the Mechanistic Evidence Show?

Merola pointed to long-standing animal data. TNF-deficient mice die of Mycobacterium tuberculosis infection, whereas selectively blocking the IL-17 and IL-23 pathways does not appear to impair the host’s control of the organism. Other models, including some human data, support that conclusion, as does clinical evidence that later segments of the series will cover.

Why Does Unnecessary Testing Matter in Practice?

Beyond the science, Merola emphasized the practical toll of routine testing. It adds burden for practices and patients, adds cost to the health system, and delays the start of treatment. He also noted that testing requirements can give payers a reason to hold up access to effective therapies. He has built a dot phrase referencing the statement into his Epic notes and points others to the paper whenever possible.