Revised Algorithmic Approach to Differentiate Between Nonspecific and Specific Etiologies of Chronic Terminal Ileitis.

Introduction: Chronic isolated terminal ileitis (TI) may be seen in Crohn's disease (CD) and intestinal tuberculosis (ITB) in addition to other etiologies that may be managed symptomatically. We developed a revised algorithm to distinguish patients with a specific etiology from a nonspecific etiology.

Methods: Patients with chronic isolated TI followed up from 2007 to 2022 were retrospectively reviewed. A specific (ITB or CD) diagnosis was made based on standardized criteria, and other relevant data were collected. Using this cohort, validation of a previously suggested algorithm was conducted. Furthermore, based on the results of a univariate analysis, a multivariate analysis with bootstrap validation was used to develop a revised algorithm.

Results: We included 153 patients (mean age 36.9 ± 14.6 years, males-70%, median duration-1.5 years, range: 0-20 years) with chronic isolated TI of whom 109 (71.2%) received a specific diagnosis (CD-69, ITB-40). On multivariate regression and validation statistics with a combination of clinical, laboratory, radiological, and colonoscopic findings, an optimism corrected c-statistic of 0.975 and 0.958 was obtained with and without histopathological findings, respectively. Revised algorithm, based on these, showed sensitivity, specificity, positive and negative predictive values, and overall accuracy of 98.2% (95% CI: 93.5-99.8), 75.0% (95% CI: 59.7-86.8), 90.7% (95% CI: 85.4-94.2), 94.3% (95% CI: 80.5-98.5) and 91.5%(95% CI:85.9-95.4), respectively. This was more sensitive and specific than the previous algorithm (accuracy 83.9%, sensitivity 95.5%, and specificity 54.6%).

Discussion: We developed a revised algorithm and a multimodality approach to stratify patients with chronic isolated TI into specific and nonspecific etiologies with an excellent diagnostic accuracy, which could potentially avoid missed diagnosis and unnecessary side effects of treatment.