Clinical value of interferon-γ release assay in the diagnosis of active tuberculosis

Navigating Diagnostic Pitfalls: False Positivity in GeneXpert Mycobacterium Tuberculosis/Rifampicin Assay

Tuberculosis (TB), which is predominantly caused by Mycobacterium tuberculosis (MTB), poses severe diagnostic hurdles, especially with pulmonary tuberculosis (PTB), which spreads by aerosols. Sputum culture, the gold standard for MTB diagnosis, is time-consuming, expensive, and easily contaminated. The GeneXpert MTB/RIF (Xpert) assay, a molecular diagnostic tool, can quickly detect MTB and rifampicin (RIF) resistance. However, the ability to identify both live and non-viable MTB DNA, for example, in patients with a previous history of pulmonary tuberculosis or sampling from a contaminated bronchoscope, can result in false positives, as demonstrated in this case series. We present three cases of PTB diagnosed with Xpert, each with no conventional TB symptoms.

Pulmonary tuberculosis associated acute fibrinous and organizing pneumonia: A case report and literature review

BACKGROUND

Acute fibrinous and organizing pneumonia (AFOP) is a rare histological interstitial pneumonia pattern characterized by patches of "fibrin balls" distributed within the alveoli and organizing pneumonia. Currently, there is no consensus on the diagnosis and treatment of this disease.

METHODS

We present the case of a 44-year-old male with AFOP secondary to Mycobacterium tuberculosis. We have further reviewed organizing pneumonia (OP) and AFOP caused by tuberculosis.

CONCLUSION

Tuberculosis secondary to OP or AFOP is rare and challenging to diagnose. We need to constantly adjust the treatment plan based on the patient's symptoms, test results, and response to treatment in order to arrive at an accurate diagnosis and maximize treatment efficacy.

Screening of Long Non-coding RNAs Biomarkers for the Diagnosis of Tuberculosis and Preliminary Construction of a Clinical Diagnosis Model

Background

Pathogenic testing for tuberculosis (TB) is not yet sufficient for early and differential clinical diagnosis; thus, we investigated the potential of screening long non-coding RNAs (lncRNAs) from human hosts and using machine learning (ML) algorithms combined with electronic health record (EHR) metrics to construct a diagnostic model.

Methods

A total of 2,759 subjects were included in this study, including 12 in the primary screening cohort [7 TB patients and 5 healthy controls (HCs)] and 2,747 in the selection cohort (798 TB patients, 299 patients with non-TB lung disease, and 1,650 HCs). An Affymetrix HTA2.0 array and qRT-PCR were applied to screen new specific lncRNA markers for TB in individual nucleated cells from host peripheral blood. A ML algorithm was established to combine the patients’ EHR information and lncRNA data via logistic regression models and nomogram visualization to differentiate PTB from suspected patients of the selection cohort.

Results

Two differentially expressed lncRNAs (TCONS_00001838 and n406498) were identified (p < 0.001) in the selection cohort. The optimal model was the “LncRNA + EHR” model, which included the above two lncRNAs and eight EHR parameters (age, hemoglobin, lymphocyte count, gamma interferon release test, weight loss, night sweats, polymorphic changes, and calcified foci on imaging). The best model was visualized by a nomogram and validated, and the accuracy of the “LncRNA + EHR” model was 0.79 (0.75–0.82), with a sensitivity of 0.81 (0.78–0.86), a specificity of 0.73 (0.64–0.79), and an area under the ROC curve (AUC) of 0.86. Furthermore, the nomogram showed good compliance in predicting the risk of TB and a higher net benefit than the “EHR” model for threshold probabilities of 0.2–1.

Conclusion

LncRNAs TCONS_00001838 and n406498 have the potential to become new molecular markers for PTB, and the nomogram of “LncRNA + EHR” model is expected to be effective for the early clinical diagnosis of TB.

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

AIM

The aim of this study was to investigate the significance of positive tuberculosis interferon gamma release assay (TB-IGRA) in the differential diagnosis of intestinal tuberculosis (ITB) and Crohn's disease (CD) patients, and to find a suitable threshold to help distinguishing CD from tuberculosis (TB), so as to provide better recommendations for clinical treatment.

METHODS

A retrospective study was performed including 484 patients who underwent TB-IGRA testing for suspected CD or ITB treated in the Shanghai Tenth People's Hospital of Tongji University between January 2015 and May 2018. According to the diagnostic criteria, 307 patients, including 272 CD and 35 ITB patients, were recruited for the final analysis. We comprehensively and systematically collected their clinical manifestations, and analyzed the influence of TB-IGRA values referring to diagnosis criteria, and the possible causes of false positives. The receiver operator characteristic (ROC) curve and the cut-off value were applied to distinguish between ITB and CD patients.

RESULTS

Of the 56 patients with suspected CD enrolled, 23 were finally diagnosed with CD and 33 with ITB. In patients with TB-IGRA ⩾ 100 pg/ml, 4 cases were CD and 29 cases were ITB, while 19 cases were CD and 4 cases were ITB in patients with TB-IGRA < 100 pg/ml (p < 0.05). TB-IGRA ⩾ 100 pg/ml indicated a high possibility of TB infection, with a sensitivity of 88% and a specificity of 74%. Three out of the four CD patients with TB-IGRA ⩾ 100 pg/ml had a history of tuberculosis, while only 1 of the 19 CD patients with TB-IGRA < 100 pg/ml had a history of tuberculosis (p < 0.05). The average duration of ITB was 7 months, and that of CD was 46.8 months, thus a significant difference (p < 0.05) was observed. Perianal lesions such as anal fistula or abscess were found in all CD patients. Among ITB patients, 8 out of 15 patients with TB-IGRA ⩾ 400 pg/ml experienced weight loss, while only 1 out of 18 patients with TB-IGRA < 400 pg/ml underwent weight loss (p < 0.05).

CONCLUSION

Patients with CD have longer duration of disease, and perianal lesions are more common in CD. ITB patients with TB-IGRA ⩾ 400 pg/ml experience weight loss more readily, which indicates that TB-IGRA value may be correlated positively with the severity of ITB. In patients with CD and ITB, TB-IGRA = 100 pg/ml may be a cut-off value of TB-IGRA. For patients with TB-IGRA ⩾ 100 pg/ml, it is recommended to use diagnostic anti-TB treatment first. Comprehensive analysis and judgment are required for patients with TB-IGRA from 14 pg/ml to 99 pg/ml. TB-IGRA false positivity may occur in patients with a history of TB infection.

Retrospective analysis of patients with non-tuberculous mycobacteria from a primary hospital in Southeast China

To achieve a comprehensive understanding of the characteristics of patients with non-tuberculous mycobacteria (NTM), patients with NTM between January 2016 and June 2019 were recruited from a primary hospital. NTM were identified based on the MBP64 protein assay. The clinical records and laboratory assay results were retrospectively reviewed. A total of 204 patients with NTM were included in the final analysis. The patients with multiple isolations were more likely accompanied with chronic obstructive pulmonary disease (COPD) (p = 0.029) and arthritis (p = 0.049), but showed a lower percentage of positive T-spot results (p = 0.022). In addition, patients with multiple isolations showed a higher rate of positive acid-fast staining results and their symptom duration was more likely longer than 30 days (p = 0.019). Patients with a positive response in T-spot assay showed a higher proportion of nodular manifestation on computed tomography (CT) than those with a negative response. Compared with male patients with NTM, female patients showed lower rates of positive acid-fast staining results (p = 0.03), but were more likely accompanied with COPD (p < 0.0001). The positive acid-fast staining results were closely associated with pulmonary cavities and tuberculosis antibody. Patients with different NTM isolation frequencies were closely associated with coexisting diseases and examination results.