CORRECTED-New model accurately differentiates intestinal tuberculosis from Crohn's disease

Last Updated: 2017-02-07

(Corrects URL in para 7.)

By Will Boggs MD

NEW YORK (Reuters Health) – A new model based on meta-analyses of 55 distinct predictors accurately differentiates intestinal tuberculosis (ITB) from Crohn's disease (CD).

"While each test is helpful, none is strong enough to be definitive,” Dr. Peter D. R. Higgins from the University of Michigan, Ann Arbor, told Reuters Health by email. “But the model as a whole can combine the effects of multiple tests into a very powerful case for either CD or TB in many cases.”

Differentiating ITB from CD is a special challenge in regions where ITB is prevalent and CD incidence is increasing. Current tests have low sensitivities, so some guidelines recommend empirical antituberculosis treatment for patients with diagnostic uncertainty, which can delay much-needed treatment for those who actually have CD.

Dr. Higgins and colleagues used 55 meta-analyses of factors predictive of ITB or CD based on published data to develop Bayesian models for discriminating IDB from CD using these factors along with the local pretest probability.

The best model incorporated demographic data and clinical manifestations, endoscopic findings, pathological findings, CT enterography findings, and serological tests.

At the cut-point of 85.83% of the probability of ITB, the model differentiated ITB from CD with a sensitivity of 90%, a specificity of 92.6%, a positive predictive value of 90.9%, a negative predictive value of 92.6%, and an accuracy of 91.8%, the researchers report in The American Journal of Gastroenterology, online January 3.

The researchers have provided this model as a web application, available here: bit.ly/ITBvsCD.

“Using the website, anyone can apply the available data they have to a particular case, and determine whether they have a strong case for CD or TB, or are still in a gray zone,” Dr. Higgins said. “They can also determine the value of additional tests (whether positive or negative), which may help them decide whether to do expensive tests like interferon-gamma testing.”

“While this has been validated in Thailand, we invite physicians in high TB prevalence areas to validate the performance of the model in their local region,” Dr. Higgins said.

Dr. Ajit Sood from Dayanand Medical College and Hospital in Ludhiana, India, who has previously investigated the differential diagnosis of Crohn's disease versus ileal tuberculosis, told Reuters Health by email, "The interesting aspect in the present article is that the model has high diagnostic accuracy. However, the difficult part is that so many parameters are considered and all these may not always be available.”

“The important point to remember is that if differentiation between the two diseases is not certain, then one should start treatment for ITB first (never for both together),” he said. “One can repeat investigations like colonoscopy at week 12 of treatment to assess endoscopic healing with antituberculosis therapy. Persistence of disease will definitely go in favor of CD.”

SOURCE: http://bit.ly/2jw6C7W

Am J Gastroenterol 2017.