SL Lapp et. al. Clin Gastroenterol Hepatol 2024; 22: 420-422. Open Access! Yield of Serial Testing for Tuberculosis Exposure in Patients With Inflammatory Bowel Diseases: One Test is Not Enough
This “retrospective cohort study was conducted using data acquired from SPARC IBD, a component of the Crohn’s & Colitis Foundation’s IBD Plexus research platform. SPARC IBD is a prospective cohort study conducted at 18 US centers and includes more than 4000 patients.” The median patient age was 37 years.
Key findings:
- Following an initial negative result in 687 patients, 269 patients received a second test (after an initial negative test), of which 5 were positive (1.9%), which was not significantly different from the prevalence with the first test
- Oral steroids were associated with an increased proportion of indeterminate results, although not achieving statistical significance
- The authors did not identify any potential risk factors for latent tuberculosis among the covariates investigated
Overall, the authors found “found that there is continued utility for the use of IGRA tests with patients receiving medication for IBD despite the declining incidence of tuberculosis in the United States. In addition to testing before administration of treatment, this study suggests serial testing may still be necessary because of a substantial rate of positive conversions among patients in the cohort.”
After reading this study, I did an informal survey from the physicians/APP in my group. As a group, we take care of approximately 1000 children with inflammatory bowel disease. Over the last 20 years, only one of my partners recollects having a true positive test result after an initial negative result. This particular patient who was asymptomatic received a 9 month course of isoniazid.
My take: There is a low yield of follow-up testing for tuberculosis, especially in pediatric patients with no exposure history or travel history. For our practice, this would be a good summer research project for a premed student, a resident or even a fellow. I would expect the yearly and cumulative costs of screening for latent tuberculosis in our practice to be quite high. A quick web search suggests that a single blood test costs ~$150 which would be $105,000 for 700 tests. However, the costs are much greater due to additional investigations related to indeterminate results.
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