Introduction: Current guidelines differ on screening for latent tuberculosis (LTB) infection prior to starting immunosuppressive therapy. We developed a Markov state-transition model to determine the most “cost-effective” screening strategy prior to initiating steroid treatment in a 5 year old with newly diagnosed idiopathic nephrotic syndrome.
Methods: Using data from the published literature, universal purified protein derivative (PPD) testing was compared with targeted screening using a risk-factor questionnaire. A secondary model also included testing with the newer interferon gamma release assays (IGRAs), requiring only a single visit and having greater specificity than the PPD.
Results: At an LTB prevalence of 1.1%, universal PPD testing was more costly and less effective than other strategies. Instead, we found that a targeted strategy using a simple risk assessment questionnaire to determine who should receive a PPD cost roughly $44,000 per quality-adjusted life year (QALY) gained compared to a no screening strategy. Conversely, at an LTB prevalence >12.8%, universal PPD became “cost-effective” compared to targeted screening. In the secondary model, targeted screening with a questionnaire followed by IGRA testing was the preferred strategy.
Conclusion: Patients who live in areas with a higher prevalence of LTB will likely benefit from universal PPD testing. Once IGRA testing is approved in children, it may become a component of “cost-effective” screening options.