TB Testing in Endemic Regions, Combination Therapy, and Broader DMARDs

A joint position statement from the National Psoriasis Foundation (NPF) and the International Psoriasis Council (IPC) questions routine tuberculosis (TB) testing with interleukin (IL)-17 and IL-23 inhibitors. It is not, however, a blanket rule against testing. In the fourth segment of this HCPLive Special Report, 2 of the statement’s co-authors clarified where testing may still be appropriate.

They were Andrew Blauvelt, MD, MBA, adjunct professor in the Department of Dermatology at the University of Maryland School of Medicine, and Joseph F. Merola, MD, MMSc, chair of the Department of Dermatology at UT Southwestern Medical Center.

Does the Statement Mean Clinicians Should Never Test for TB?

Blauvelt explained that the NPF Medical Board, made up of about 35 members based in the US and Canada, approved the statement unanimously. Among IPC experts, 87% voted in favor and 13% against. The members who voted against practice in regions where TB is endemic and routinely test before starting any biologic. Blauvelt said testing remains reasonable in those settings, particularly when a dermatologist is the patient’s only clinician.

He compared it to checking lipids or blood pressure as part of comprehensive care. Many such patients are also taking or switching from tumor necrosis factor (TNF) inhibitors and need testing regardless. The key point, he said, is that IL-17 and IL-23 inhibitors do not make reactivation more likely. He compared them to doxycycline for acne: clinicians would not screen for TB before prescribing it, even in areas where TB is common.

How Does the Statement Apply Across Specialties?

Merola noted that the statement matters beyond dermatology, including in rheumatology. There, TB testing is especially reflexive because TNF inhibitors remain heavily used, often alongside conventional disease-modifying antirheumatic drugs (DMARDs). Low-dose methotrexate alone carries a small risk of reactivation. For that reason, he emphasized that the statement addresses IL-17 and IL-23 inhibitors used alone, with decisions made case by case. He described strong enthusiasm among audiences and residents, who are glad to stop chasing down TB test results and the treatment delays that follow.

Which Other Therapies Still Warrant Screening?

Asked about other agents, Merola said JAK inhibitors carry a meaningful, observed risk of TB reactivation, so screening is warranted. Leflunomide has been studied in combination regimens for psoriatic arthritis. Its risk is less clearly quantified, but some observational studies show an association, so screening is worth considering. Azathioprine may also carry some risk. For these broader-acting agents, he said testing is reasonable. That contrast, he added, shows why the statement was grounded in both mechanism and clinical data.