Levels of TB-IGRA may help to differentiate between intestinal tuberculosis and Crohn's disease in patients with positive results

New diagnostic strategies to distinguish Crohn's disease and gastrointestinal tuberculosis

PURPOSE OF REVIEW

Despite advances in our radiological, histological and microbiological armamentarium, distinguishing between Crohn's disease (CD) and intestinal tuberculosis (ITB), especially in a TB endemic country, continues to be a challenging exercise in a significant number of patients. This review aims to summarize current available evidence on novel diagnostic techniques which have a potential to fill the gap in our knowledge of differentiating between ITB and CD.

RECENT FINDINGS

Both ITB and CD are associated with altered host immune responses, and detection of these altered innate and adaptive immune cells has potential to distinguish ITB from CD. ITB and CD have different epigenetic, proteomic and metabolomic signatures, and recent research has focused on detecting these differences. In addition, the gut microbiome, which is involved in mucosal immunity and inflammatory responses, is considerably altered in both ITB and CD, and is another potential frontier, which can be tapped to discriminate between the two diseases. With technological advancements, we have newer radiological modalities including perfusion CT and dual-layer spectral detector CT enterography and evidence is emerging of their role in differentiating ITB from CD. Finally, time will tell whether the advent of artificial intelligence, with rapidly accumulating data in this field, will be the gamechanger in solving this puzzle of diagnostic dilemma between ITB and Crohn's disease.

SUMMARY

Recent advances need to be clinically validated before they can be used as novel diagnostic measures to differentiate Intestinal TB from CD.

Interferon-gamma release assays as a tool for differential diagnosis of gastrointestinal tuberculosis

In this editorial, we comment on an article published in a recent issue of the World Journal of Clinical Cases. There is a pressing need for reliable tools for diagnosing tuberculosis (TB) of the gastrointestinal tract. Despite advancements in the diagnosis and treatment, TB remains a global health challenge. Ali et al demonstrated that TB may mimic gastrointestinal conditions, such as gastric outlet obstruction, causing a delay in the diagnosis. Furthermore, the latter complication is frequently observed during infections, including Helicobacter pylori, and rarely is related to TB, as in the presented case. In line with this, we think that laboratory tests based on interferon-gamma release assays can be a helpful tool for diagnosing latent TB paced in the gastrointestinal tract. Innovative strategies and approaches for diagnosing latent/active extra pulmonary TB are crucial for establishing the diagnosis early and enhancing treatment strategies to mitigate the global burden of TB.

Asymptomatic intestinal tuberculosis of the terminal ileum diagnosed on colonoscopy: a case report and literature review

Objective

Colonoscopy is useful in diagnosing intestinal tuberculosis. However, the terminal ileum is generally not examined during routine colonoscopy. Therefore, even with colonoscopy, the diagnosis can be missed in patients with lesions confined to the terminal ileum. Herein, we report the case of an asymptomatic patient with intestinal tuberculosis, in whom a colonoscope insertion into the terminal ileum led to the diagnosis.

Patient

An asymptomatic 71-year-old man visited our hospital for a colonoscopy after a positive fecal occult blood test.

Results

Colonoscopy revealed diffuse edematous and erosive mucosa in the terminal ileum. Mycobacterium tuberculosis was detected by polymerase chain reaction and culture of biopsy specimens from the erosions, leading to the diagnosis of intestinal tuberculosis. The patient was treated with antitubercular agents for 6 months, and a follow-up colonoscopy revealed healing of the lesions.

Conclusion

Asymptomatic intestinal tuberculosis may occasionally be detected on colonoscopy following a positive fecal occult blood test and is sometimes confined to the terminal ileum. Therefore, clinicians should consider intestinal tuberculosis in the differential diagnosis of the causes of positive fecal occult blood test results and perform colonoscopies, including observation of the terminal ileum.

Diagnostic accuracy of the IFN-γ release assay using RD1 immunodominant T-cell antigens for diagnosis of extrapulmonary tuberculosis

The diagnosis of extrapulmonary tuberculosis (EPTB) poses a significant challenge, with controversies surrounding the accuracy of IFN-γ release assays (IGRAs). This study aimed to assess the diagnostic accuracy of RD1 immunodominant T-cell antigens, including ESAT-6, CFP-10, PE35, and PPE68 proteins, for immunodiagnosis of EPTB. Twenty-nine patients with EPTB were enrolled, and recombinant PE35, PPE68, ESAT-6, and CFP-10 proteins were evaluated in a 3-day Whole Blood Assay. IFN-γ levels were measured using a Human IFN-γ ELISA kit, and the QuantiFERON-TB Gold Plus (QFT-Plus) test was performed. Predominantly, the patients were of Afghan (62%, n = 18) and Iranian (38%, n = 11) nationalities. Eighteen individuals tested positive for QFT-Plus, accounting for 62% of the cases. The positivity rate for IGRA, using each distinct recombinant protein (ESAT-6, PPE68, PE35, and CFP-10), was 72% (n = 21) for every protein tested. Specifically, among Afghan patients, the positivity rates for QFT-Plus and IGRA using ESAT-6, PPE68, PE35, and CFP-10 were 66.7%, 83.3%, 83.3%, 77.8%, and 88.9%, respectively. In contrast, among Iranian patients, the positivity rates for the same antigens were 54.5%, 54.5%, 54.5%, 63.6%, and 45.5%, respectively. In conclusion, our study highlights the potential of IGRA testing utilizing various proteins as a valuable diagnostic tool for EPTB. Further research is needed to elucidate the underlying factors contributing to these disparities and to optimize diagnostic strategies for EPTB in diverse populations.

Intestinal flora altered and correlated with interleukin-2/4 in patients with primary immune thrombocytopenia

BACKGROUND

Little is known about the changes and mechanisms of intestinal flora in primary immune thrombocytopenia (ITP) patients.

AIM

To explore the structural and functional differences of intestinal flora between ITP patients and healthy controls, and clarify the correlation between intestinal flora and Th1/Th2 imbalance.

METHODS

Feces from ITP patients and healthy controls were studied by 16S rRNA and metagenomic techniques at phylum, genus, species or functional levels. Blood samples were collected for the detection of interleukin -2 (IL-2) and IL-4 concentrations.

RESULTS

The following changes in ITP patients were found: a decrease of Bacteroidetes phylum, an increase of Proteobacteria phylum and alterations of ten genera and 1045 species. IL-2 and IL-4 were significantly correlated with six and five genera, respectively. Species of C. freundii, C. rodentium, and C. youngae were negatively correlated with bleeding scores, and S. infantis was positively related to platelet counts. Functionally, the intestinal flora of ITP patients changed mainly in terms of motility, chemotaxis, membrane transport, and metabolism.

CONCLUSION

The mechanism underlying functional and structural changes of intestinal flora in ITP patients may be related to inflammation and immunity, providing possibilities of probiotics or fecal transplants for ITP.

Differentiating gastrointestinal tuberculosis and Crohn's disease- a comprehensive review

Gastrointestinal Tuberculosis (GITB) and Crohn's disease (CD) are both chronic granulomatous diseases with a predilection to involve primarily the terminal ileum. GITB is often considered a disease of the developing world, while CD and inflammatory bowel disease are considered a disease of the developed world. But in recent times, the epidemiology of both diseases has changed. Differentiating GITB from CD is of immense clinical importance as the management of both diseases differs. While GITB needs anti-tubercular therapy (ATT), CD needs immunosuppressive therapy. Misdiagnosis or a delay in diagnosis can lead to catastrophic consequences. Most of the clinical features, endoscopic findings, and imaging features are not pathognomonic for either of these two conditions. The definitive diagnosis of GITB can be clinched only in a fraction of cases with microbiological positivity (acid-fast bacilli, mycobacterial culture, or PCR-based tests). In most cases, the diagnosis is often based on consistent clinical, endoscopic, imaging, and histological findings. Similarly, no single finding can conclusively diagnose CD. Multiparametric-based predictive models incorporating clinical, endoscopy findings, histology, radiology, and serology have been used to differentiate GITB from CD with varied results. However, it is limited by the lack of validation studies for most such models. Many patients, especially in TB endemic regions, are initiated on a trial of ATT to see for an objective response to therapy. Early mucosal response assessed at two months is an objective marker of response to ATT. Prolonged ATT in CD is recognized to have a fibrotic effect. Therefore, early discrimination may be vital in preventing the delay in the diagnosis of CD and avoiding a complicated course.

Evidence-based approach to diagnosis and management of abdominal tuberculosis

Abdominal tuberculosis is an ancient problem with modern nuances in diagnosis and management. The two major forms are tuberculous peritonitis and gastrointestinal tuberculosis (GITB), while the less frequent forms are esophageal, gastroduodenal, pancreatic, hepatic, gallbladder and biliary tuberculosis. The clinicians need to discriminate the disease from the close mimics: peritoneal carcinomatosis closely mimics peritoneal tuberculosis, while Crohn's disease closely mimics intestinal tuberculosis. Imaging modalities (ultrasound, computed tomography, magnetic resonance imaging and occasionally positron emission tomography) guide the line of evaluation. Research in diagnostics (imaging and endoscopy) has helped in the better acquisition of tissue for histological and microbiological tests. Although point-of-care polymerase chain reaction-based tests (e.g. Xpert Mtb/Rif) may provide a quick diagnosis, these have low sensitivity. In such situations, ancillary investigations such as ascitic adenosine deaminase and histological clues (granulomas, caseating necrosis, ulcers lined by histiocytes) may provide some specificity to the diagnosis. A diagnostic trial of antitubercular therapy (ATT) may be considered if all diagnostic armamentaria fail to clinch the diagnosis, especially in TB-endemic regions. Objective evaluation with clear endpoints of response is mandatory in such situations. Early mucosal response (healing of ulcers at two months) and resolution of ascites are objective criteria for early response assessment and should be sought at two months. Biomarkers, especially fecal calprotectin for intestinal tuberculosis, have also shown promise. For most forms of abdominal tuberculosis, six months of ATT is sufficient. Sequelae of GITB may require endoscopic balloon dilatation for intestinal strictures or surgical intervention for recurrent intestinal obstruction, perforation or massive bleeding.

Applying logistic LASSO regression for the diagnosis of atypical Crohn's disease

In countries with a high incidence of tuberculosis, the typical clinical features of Crohn's disease (CD) may be covered up after tuberculosis infection, and the identification of atypical Crohn's disease and intestinal tuberculosis (ITB) is still a dilemma for clinicians. Least absolute shrinkage and selection operator (LASSO) regression has been applied to select variables in disease diagnosis. However, its value in discriminating ITB and atypical Crohn's disease remains unknown. A total of 400 patients were enrolled from January 2014 to January 2019 in second Xiangya hospital Central South University.Among them, 57 indicators including clinical manifestations, laboratory results, endoscopic findings, computed tomography enterography features were collected for further analysis. R software version 3.6.1 (glmnet package) was used to perform the LASSO logistic regression analysis. SPSS 20.0 was used to perform Pearson chi-square test and binary logistic regression analysis. In the variable selection step, LASSO regression and Pearson chi-square test were applied to select the most valuable variables as candidates for further logistic regression analysis. Secondly, variables identified from step 1 were applied to construct binary logistic regression analysis. Receiver operating characteristic (ROC) curve analysis was performed on these models to assess the ability and the optimal cutoff value for diagnosis. The area under the ROC curve (AUC), sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy rate, together with their 95% confidence and intervals (CIs) were calculated. MedCalc software (Version 16.8) was applied to analyze the ROC curves of models. 332 patients were eventually enrolled to build a binary logistic regression model to discriminate CD (including comprehensive CD and tuberculosis infected CD) and ITB. However, we did not get a satisfactory diagnostic value via applying the binary logistic regression model of comprehensive CD and ITB to predict tuberculosis infected CD and ITB (accuracy rate:79.2%VS 65.1%). Therefore, we further established a binary logistic regression model to discriminate atypical CD from ITB, based on Pearsonchi-square test (model1) and LASSO regression (model 2). Model 1 showed 89.9% specificity, 65.9% sensitivity, 88.5% PPV, 68.9% NPV, 76.9% diagnostic accuracy, and an AUC value of 0.811, and model 2 showed 80.6% specificity, 84.4% sensitivity, 82.3% PPV, 82.9% NPV, 82.6% diagnostic accuracy, and an AUC value of 0.887. The comparison of AUCs between model1 and model2 was statistically different (P < 0.05). Tuberculosis infection increases the difficulty of discriminating CD from ITB. LASSO regression showed a more efficient ability than Pearson chi-square test based logistic regression on differential diagnosing atypical CD and ITB.

Recent advances in the diagnosis of intestinal tuberculosis

BACKGROUND

Intestinal tuberculosis still has a high incidence, especially in developing countries. The biggest challenge of this disease is the establishment of the diagnosis because the clinical features are not typical. Investigations such as culture, acid-fast bacilli (AFB) staining, and histopathology have low sensitivity, so other investigations are needed. Latest molecular-based diagnostic modalities such as GeneXpert, interferon-gamma (IFN-γ) release assays (IGRA), polymerase chain reaction (PCR), multiplex-PCR, and immunological markers are expected to help diagnose intestinal tuberculosis. This article review will examine the latest diagnostic modalities that can be used as a tool in establishing the diagnosis of intestinal tuberculosis.

RESULTS

Through a literature search, we were able to review the diagnostic values of various available diagnostic modalities as the appropriate additional test in intestinal tuberculosis. Culture as a gold standard has a sensitivity and specificity value of 9.3% and 100% with the MGIT BACTEC system as the most recommended medium. The sensitivity values of AFB staining, histopathology examination, GeneXpert, IGRA, PCR, multiplex-PCR and, immunological markers were ranged between 17.3 and 31%; 68%; 81-95.7%; 74-88%; 21.6-65%; 75.7-93.1%; and 52-87%, respectively. Meanwhile the specificity values were 100%; 77.1%; 91-100%; 74-87%; 93-100%; 96.4-100%; and 70-95%, respectively.

CONCLUSION

The combination of clinical examination, conventional examination, and the latest molecular-based examination is the best choice for establishing the diagnosis of intestinal tuberculosis. Most recent modalities such as multiplex PCR and immunological marker examinations are diagnostic tools that deserve to be used in diagnosing intestinal tuberculosis as their sensitivity and specificity values are quite high and more evidences are expected to support the application of these examinations shortly soon.

Recent updates in diagnosis of abdominal tuberculosis with emphasis on nucleic acid amplification tests

INTRODUCTION

Abdominal tuberculosis (TB) is a common epitome of extrapulmonary TB (EPTB), wherein peritoneal and intestinal TB are the most prevalent forms. Diagnosis of abdominal TB is a daunting challenge owing to variable anatomical locations, paucibacillary nature of specimens and atypical clinical presentations that mimic other abdominal diseases, such as Crohn's disease and malignancies. In this review, we made a comprehensive study on the diagnosis of abdominal TB.

AREA COVERED

Various modalities employed for abdominal TB diagnosis include clinical features, imaging, bacteriological tests (smear/culture), histopathological/cytological observations, interferon-gamma release assays and nucleic acid amplification tests (NAATs). Among NAATs, loop-mediated isothermal amplification assay, PCR, multiplex-PCR, nested PCR, real-time PCR and GeneXpert® MTB/RIF were discussed. Identification of circulating Mycobacterium tuberculosis cell-free DNA by real-time PCR within ascitic fluids is another useful approach.

EXPERT OPINION

Several novel molecular/immunological methods, such as GeneXpert Ultra, aptamer-linked immobilized sorbent assay, immuno-PCR (I-PCR) and nanoparticle-based I-PCR have recently been developed for detecting pulmonary TB and several EPTB types, which may also be explored for abdominal TB diagnosis. Precise and prompt diagnosis of abdominal TB may initiate an early therapy so as to reduce the complications, i.e. abdominal pain, ascites, abdominal distension, intestinal obstruction/perforation, etc., and avoid surgical involvement.Plain Language SummaryAbdominal tuberculosis (TB) is a manifestation of extrapulmonary TB (EPTB), where peritoneal and intestinal TB are two major forms. Diagnosis of abdominal TB is difficult owing to low bacterial load present in clinical samples and non-specific clinical presentations as it mimics other diseases such as inflammatory bowel diseases, abdominal malignancies, etc. Bacteriological tests (smear/culture) almost fail owing to poor sensitivities and it is not always possible to get representative tissue samples for histopathological and cytological observations. In recent years, molecular tests i.e. nucleic acid amplification tests (NAATs), such as PCR/multiplex-PCR (M-PCR), nested PCR and GeneXpert are widely employed. Markedly, PCR/M-PCR and nested PCR exhibited reasonable good sensitivities/specificities, while GeneXpert revealed low sensitivity in most of the studies but high specificity, thus it could assist in differential diagnosis of intestinal TB and Crohn's disease. Further, novel molecular/immunological tests employed for pulmonary TB and other EPTB types were described and those tests can also be utilized to diagnose abdominal TB. Reliable and rapid diagnosis of abdominal TB would initiate an early start of anti-tubercular therapy and reduce the severe complications.

A Novel Clinical Radiomics Nomogram to Identify Crohn's Disease from Intestinal Tuberculosis

Purpose

To establish a clinical radiomics nomogram to differentiate Crohn’s disease (CD) from intestinal tuberculosis (ITB).

Patients and Methods

Ninety-three patients with CD and 67 patients with ITB were recruited (111 in training cohort and 49 in test cohort). The region of interest (ROI) for the lesions in the ileocecal region was delineated on computed tomography enterography and radiomics features extracted. Radiomics features were filtered by the gradient boosting decision tree (GBDT), and a radiomics score was calculated by using the radiomics signature-based formula. We constructed a clinical radiomics model and nomogram combining clinical factors and radiomics score through multivariate logistic regression analysis, and the internal validation was undertaken by ten-fold cross validation. Analyses of receiver operating characteristic (ROC) curves and decision curve analysis (DCA) were used to evaluate the prediction performance. DeLong test was applied to evaluate the performance of the clinical, radiomics and combined model.

Results

The clinical radiomics nomogram, which was based on the 9 radiomics signature and two clinical factors, indicated that the clinical radiomics model had an area under the ROC curve (AUC) value of 0.96 (95% confidence interval [CI]: 0.93–0.99) in the training cohort and 0.93 (95% CI: 0.86–1.00) in validation cohort. The clinical radiomics model was superior to the clinical model and radiomics model, and the difference was significant (P = 0.006, 0.004) in the training cohort. DCA confirmed the clinical utility of clinical radiomics nomogram.

Conclusion

CTE-based radiomics model has a good performance in distinguishing CD from ITB. A nomogram constructed by combining radiomics and clinical factors can help clinicians accurately diagnose and select appropriate treatment strategies between CD and ITB.