important and likely diagnoses Healthy small intestine Crohn’s disease ulceration Intestinal TB ulceration Treat with immune suppression Treat with antimicrobials Wrong Rx – antimicrobials – very, very sick Wrong Rx – immune suppression – very, very sick or DEAD TREATMENT: WRONG DIAGNOSIS:
on small bowel ulceration: • If unsure whether intestinal TB (ITB) vs. Crohn’s disease, Empirically treat with 4 anti-tuberculous therapies for 8-12 weeks. • If not improved, likely to be Crohn’s disease • During the 8-12 weeks, patients can experience worsening bleeding, weight loss, fatigue, intestinal blockages, nausea/vomiting, and intestinal perforation – may progress to surgery Ooi CJ , Hilmi I , Makharia GK et al. The Asia Pacific Consensus Statements on Crohn's Disease Part 1: definition, diagnosis and epidemiology. J Gastroenterol Hepatol 2015; 31: 45–55.
have data available The relative prevalence of ITB ( !"# !"#$%& ) Probability of ITB = ( ) ∗(,- . ∗,- / ∗⋯ ) .2( ) $(( ) ∗,- . ∗,- / ∗⋯ ) For findings without available results, the model defaults to an LR of 1 for that finding
to sequential models • Clinical model • Endoscopy model • Clinical + endoscopy model • Clinical + endoscopy + pathology model • The performance of the model was determined by • area under the curve of receiver operating characteristic curves • sensitivity, specificity, accuracy, false positive & negative rate
https://www.pathology.med.umich.edu/shiny/tbcrohns/ - Robust to incomplete data - Computes estimates immediately - Allows user to evaluate the effects of additional (sometimes expensive) testing - Now frequently use in Asia
a dichotomous choice • Medicine is often not dichotomous • Patient with weight loss and hemoccult + stool • Strange-looking ulceration in small intestine on scope • Biopsies: ulceration, nonspecific inflammation, and healing • Model suggests more likely to be TB • All TB tests negative • ??? • Re-scope, more biopsies with depth – small bowel adenocarcinoma
make models useful at the point of care • Can not be definitive • It helps to be robust to missing data • Always consider edge cases! • Manuscript: Limsrivilai, J., Am J Gast. 2017; 112: 415-427. https://www.ncbi.nlm.nih.gov/pubmed/28045023 • Shiny app: https://www.pathology.med.umich.edu/shiny/tbcrohns/