TB screening before IL-17 and IL-23 biologics still earns its place in high-burden settings

Design

Retrospective multicentre score development and validation

Population

Adults with psoriasis starting biologics, four Chinese hospitals

Primary outcome

High pre-treatment IGRA response

Effect

AUC 0.80 development, 0.70 validation, 0.62 external; high-risk positivity 14–33%

A retrospective study from four Chinese hospitals included adults with psoriasis about to start biologic therapy and developed a six-item score to predict a high pre-treatment interferon-γ release assay (IGRA) response. The items were age over 43, BMI over 24.8, being married, smoking, alcohol use and, as a negative item, acitretin use.

Discrimination was fair in the development cohort (AUC 0.80) but fell in validation (0.70) and in a geographically distinct cohort (0.62). IGRA positivity in the high-risk group was 14–33% across cohorts, and even the low-risk group had about 3%.

Some low-burden-country guidance allows routine TB testing to be dropped before IL-17 and IL-23 inhibitors. This study's authors argue that is unsafe where TB is common, and the positivity rates support them. In India, the practical message is not to adopt the score but to keep screening everyone, and to use risk factors to decide who needs closer follow-up.

• Screen for latent TB with IGRA or tuberculin skin test before any biologic, including IL-17 and IL-23 inhibitors, in high-burden settings
• Take a TB exposure history and chest radiograph alongside the blood test
• Treat latent TB per national guidance before or alongside starting a biologic
• Consider smoking, alcohol and higher BMI as flags for closer TB vigilance during treatment
• Do not use this score to skip testing; it has not been validated outside China

Why it matters

Low-burden exemptions from TB testing do not travel to countries where latent infection is common.

Don't overread it

The score predicts a blood test result, not active TB, and lost accuracy outside its development setting.

The statistics, in plain English

An AUC of 0.80 means fair discrimination, but it fell to 0.62 in a separate cohort — close to a coin toss — which is the usual fate of scores tested outside the population that built them. The study measured IGRA results, not who went on to develop TB.

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