Andrew Blauvelt, MD 

The Hidden Costs of Routine TB Testing Before IL-17 and IL-23 Inhibitors

Routine tuberculosis (TB) testing before starting interleukin (IL)-17 and IL-23 inhibitors does more than delay treatment. It causes a range of downstream harms for patients and practices. In the final segment of this 

 Special Report, 2 co-authors of the joint position statement from the National Psoriasis Foundation (NPF) and the International Psoriasis Council (IPC) outlined those harms and reflected on the statement’s impact.

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.

What Problems Can Routine TB Testing Create?

Merola described a recent patient, an older woman with no meaningful exposure risk who had rarely left her home in decades. She was tested only because her payer required it, and she received 2 indeterminate results in a row. Each round meant another hour-long drive to the clinic, which he suggested likely posed a greater risk to her than TB reactivation. It also added cost to the health system and further delayed the start of therapy.

He listed further problems: false-positive results, uncertainty about how to interpret indeterminate results, and repeated retesting. Patients are also commonly lost to follow-up. When they are tested at outside facilities, the results may never reach the prescribing office, and patients can return months later still untreated. Merola called the statement practice-changing rather than a minor adjustment.

Can TB Testing Lead to Unnecessary Treatment?

Blauvelt added that testing can also lead to unnecessary treatment for latent TB infection (LTBI). Merola agreed. He noted that as patients age, the risks of LTBI therapy, including liver toxicity, begin to outweigh its benefits. Testing an older, low-risk population can therefore trigger therapy that carries its own harms and may offer little benefit.

Blauvelt said the issue has long been a priority for him. While the phase 3 risankizumab program was being designed, he argued that TB testing was unnecessary. One of the 4 trials left testing out, but the other 3 kept it, and the requirement ended up in the label. He said the evidence is now clear and the statement, though arguably overdue, is better late than never.

Merola closed by encouraging clinicians to hold firm and push back when payers require TB testing for these agents. He noted that he has had to do so himself and hopes to see change.


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From false positives to lost follow-up and unneeded LTBI therapy, experts detail the harms of routine TB testing with IL-17 and IL-23 inhibitors in psoriasis.

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 

 Special Report, 2 of the statement’s co-authors clarified where testing may still be appropriate.

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.

The NPF/IPC TB statement isn’t a blanket no-test rule. Experts explain when screening still fits, from endemic regions to JAK inhibitors and other DMARDs.

Why the TB Testing Statement Stops Short of Ustekinumab and TYK2 Inhibitors

A joint position statement from the National Psoriasis Foundation (NPF) and the International Psoriasis Council (IPC) on tuberculosis (TB) testing focuses specifically on interleukin (IL)-17 and IL-23 inhibitors. In the third segment of this 

 Special Report, 2 of the statement’s co-authors explained why other drug classes were left out and how the statement may lead to label changes. 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.

Why Were IL-12/23 Inhibitors Excluded From the Statement?

Blauvelt noted that ustekinumab targets p40, a subunit shared by IL-12 and IL-23, whereas IL-23 inhibitors selectively block the p19 subunit. The IL-12 pathway drives T helper 1 (Th1) immunity, which is believed to be important for forming and controlling granulomas. Inhibiting that pathway could therefore impair granulomas in theory. The biology differs from that of tumor necrosis factor (TNF), however, which plays a central role in controlling TB within tissue. Some cases of TB reactivation have been reported with ustekinumab. The risk appears lower than with TNF inhibitors but is still present, which is why the authors chose not to include the drug.

Could TYK2 Inhibitors Follow the Same Path?

The same question now applies to tyrosine kinase 2 (TYK2) inhibitors. These include deucravacitinib and 2 newer agents on the way. They inhibit both IL-12 and IL-23 and work somewhat like an oral version of ustekinumab. Blauvelt said the NPF has been asked to review TB data for the class. In his view, though, the case for dropping testing is not as strong as it is for IL-17 and IL-23 inhibitors. Merola agreed. He added that TYK2 inhibition also affects type 1 interferon signaling and that the science does not yet support extending the statement to this class.

Several years ago, before the paper was written, Blauvelt met with the FDA alongside NPF representatives and Mark Lebwohl, MD. They raised the issue of TB testing with IL-17 and IL-23 inhibitors, and the agency was open to label changes based on data. Each manufacturer, however, must start such a change by petitioning the FDA. Blauvelt called the nonmandatory TB testing language in the icotrokinra label a success for the NPF and IPC effort, and he suggested future agents in these classes may follow suit. Merola said that if the statement shapes how future studies are designed, it could also support company-driven label changes for existing drugs.

Experts explain why ustekinumab and TYK2 inhibitors were excluded from new TB testing guidance and how FDA label changes for IL-17/IL-23 agents could happen.

4 Lines of Evidence Behind Dropping TB Testing for IL-17, IL-23 Inhibitors

A joint position statement from the National Psoriasis Foundation (NPF) and the International Psoriasis Council (IPC) addresses tuberculosis (TB) testing with interleukin (IL)-17 and IL-23 inhibitors. It draws on 4 distinct bodies of evidence. In the second segment of this 

 Special Report, 2 of the statement’s co-authors walked through that evidence and how newer trial designs are reinforcing it.

What Do Basic Science and Clinical Trials Show About TB Risk?

Blauvelt explained that the authors first reviewed basic science data, including mouse models. Some studies have hinted that IL-17 or IL-23 may contribute to TB pathogenesis, but he said that evidence does not hold up under close review. When IL-12 signaling is intact, it appears to be the dominant factor in TB control. IL-23 appears to play a role only when IL-12 is deficient.

The group then examined clinical trial data across all available IL-17 and IL-23 inhibitors. Blauvelt acknowledged a limitation: trial participants are selected. They must test negative for TB or be treated for latent TB infection (LTBI) before enrolling.

How Do Real-World and Postmarketing Data Support the Statement?

To address that gap, the authors turned to real-world evidence, which has grown substantially in recent years. Blauvelt noted that the passage of time is a strength of the paper, since the data needed to support the statement did not exist earlier. He said cases are essentially absent across that literature. The single reported case occurred with an IL-17 inhibitor 14 months after starting treatment, and that rate falls below the background rate of TB reactivation in the general population. The final component was the FDA Adverse Event Reporting System (FAERS), which likewise yielded virtually no cases.

How Are Newer Trials Changing the Picture?

Merola added that a prospective element now strengthens this picture. Trials of icotrokinra, an oral targeted peptide that blocks the IL-23 receptor, allowed patients with a history of LTBI to stay on treatment, and no reactivation was observed. He said the resulting label makes the drug easier for both patients and prescribers to use. He hopes this approach will influence how future studies are designed.

Merola closed the segment with a question about IL-12/23 inhibitors such as ustekinumab. These drugs were not covered in the statement but may see renewed use as biosimilars enter the market.

Basic science, trials, real-world data, and FAERS reports show little TB reactivation risk with IL-17 and IL-23 inhibitors, supporting new NPF/IPC guidance.

Andrew Blauvelt, MD

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