Nodular reverse halo sign in active pulmonary tuberculosis: A rare CT feature?

Diagnostic value of the Xpert MTB/RIF assay combined with endobronchial ultrasonography with a guide sheath for peripheral nodular pulmonary tuberculosis

BACKGROUND

The diagnosis of peripheral isolated nodular lesions that are suspected as pulmonary tuberculosis (PTB) is challenging, which are not easily accessible via conventional bronchoscopy. This study evaluated the combined use of Xpert MTB/RIF assay and endobronchial ultrasonography with a guide sheath (EBUS-GS) for detecting MTB infection in peripheral lung bands, for early detection of PTB.

METHODS

The clinical data of 232 patients with suspected peripheral nodular PTB who underwent EBUS-GS between June 2020 and October 2023 were retrospectively reviewed. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) of acid-fast bacilli smear, culture, Xpert MTB/RIF assay, and pathological examination were calculated. To assess diagnostic accuracy, the results of the four methods were directly compared with the final clinical diagnosis.

RESULTS

In total, 146 and 86 patients were clinically diagnosed with peripheral nodular PTB and non-PTB, respectively. The sensitivity, specificity, PPV, NPV, and AUC values of combined Xpert MTB/RIF assay and EBUS-GS were 47.26%, 100.0%, 100.0%, 52.76%, and 0.74; those of acid-fast bacilli smear were 8.22%, 97.67%, 85.71%, 38.53%, and 0.53; those of culture were 31.51%, 100.0%, 100.0%, 46.24%, and 0.66; and those of pathological examination were 23.97%, 97.67%, 94.59%, 43.08%, and 0.61, respectively.

CONCLUSION

The diagnostic accuracy of the combined Xpert MTB/RIF assay and EBUS-GS was significantly better than that of other conventional tests. Hence, this novel technique can be routinely applied for diagnosing and managing peripheral nodular PTB.

Reversed halo sign as a radiological feature of tuberculosis - Report of two cases

Reversed halo sign (RHS) is a radiological feature described as a focal, rounded area of ground-glass opacity surrounded by a ring of consolidation. In this report we describe two unique radiological cases demonstrating diffuse bilateral infiltrates with multiple RHSs in chest CT scans. Both patients were ultimately diagnosed as having tuberculosis (TB) and had been exposed to silica in the past. This report presents for the first time an association between silica exposure and RHS on CT scans among TB patients. It highlights the importance of having a high index of suspicion for TB in similar scenarios.

Deep learning based CT images automatic analysis model for active/non-active pulmonary tuberculosis differential diagnosis

Active pulmonary tuberculosis (ATB), which is more infectious and has a higher mortality rate compared with non-active pulmonary tuberculosis (non-ATB), needs to be diagnosed accurately and timely to prevent the tuberculosis from spreading and causing deaths. However, traditional differential diagnosis methods of active pulmonary tuberculosis involve bacteriological testing, sputum culturing and radiological images reading, which is time consuming and labour intensive. Therefore, an artificial intelligence model for ATB differential diagnosis would offer great assistance in clinical practice. In this study, computer tomography (CT) scans images and corresponding clinical information of 1160 ATB patients and 1131 patients with non-ATB were collected and divided into training, validation, and testing sets. A 3-dimension (3D) Nested UNet model was utilized to delineate lung field regions in the CT images, and three different pre-trained deep learning models including 3D VGG-16, 3D EfficientNet and 3D ResNet-50 were used for classification and differential diagnosis task. We also collected an external testing set with 100 ATB cases and 100 Non-ATB cases for further validation of the model. In the internal and external testing set, the 3D ResNet-50 model outperformed other models, reaching an AUC of 0.961 and 0.946, respectively. The 3D ResNet-50 model reached even higher levels of diagnostic accuracy than experienced radiologists, while the CT images reading and diagnosing speed was 10 times faster than human experts. The model was also capable of visualizing clinician interpretable lung lesion regions important for differential diagnosis, making it a powerful tool assisting ATB diagnosis. In conclusion, we developed an auxiliary tool to differentiate active and non-active pulmonary tuberculosis, which would have broad prospects in the bedside.

Active pulmonary tuberculosis: something old, something new, something borrowed, something blue

Tuberculosis remains a major global health issue affecting all countries and age groups. Radiology plays a crucial role in the diagnosis and management of pulmonary tuberculosis (PTB). This review aims to improve understanding and diagnostic value of imaging in PTB. We present the old, well-established findings ranging from primary TB to the common appearances of post-primary TB, including dissemination with tree-in-bud nodularity, haematogenous dissemination with miliary nodules and lymphatic dissemination. We discuss new concepts in active PTB with special focus on imaging findings in immunocompromised individuals. We illustrate PTB appearances borrowed from other diseases in which the signs were initially described: the reversed halo sign, the galaxy sign and the cluster sign. There are several radiological signs that have been shown to correlate with positive or negative sputum smears, and radiologists should be aware of these signs as they play an important role in guiding the need for isolation and empirical anti-tuberculous therapy.

The Pathogenesis of Tuberculosis-The Koch Phenomenon Reinstated

Research on the pathogenesis of tuberculosis (TB) has been hamstrung for half a century by the paradigm that granulomas are the hallmark of active disease. Human TB, in fact, produces two types of granulomas, neither of which is involved in the development of adult type or post-primary TB. This disease begins as the early lesion; a prolonged subclinical stockpiling of secreted mycobacterial antigens in foamy alveolar macrophages and nearby highly sensitized T cells in preparation for a massive necrotizing hypersensitivity reaction, the Koch Phenomenon, that produces caseous pneumonia that is either coughed out to form cavities or retained to become the focus of post-primary granulomas and fibrocaseous disease. Post-primary TB progresses if the antigens are continuously released and regresses when they are depleted. This revised paradigm is supported by nearly 200 years of research and suggests new approaches and animal models to investigate long standing mysteries of human TB and vaccines that inhibit the early lesion to finally end its transmission.

Chest CT in COVID-19 pneumonia: A review of current knowledge

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Unenhanced chest CT is indicated for patients with suspected COVID-19 presenting with dyspnea, polypnea or arterial blood oxygen desaturation.

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Most typical CT features of COVID-19 pneumonia include bilateral and multifocal ground-glass opacities predominating in the peripheral, posterior and basal parts of the lungs.

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Between 15 and 30% of hospitalized patients with COVID-19 progress to acute respiratory distress syndrome, which is the main cause of mortality.

The current COVID-19 pandemic has highlighted the essential role of chest computed tomography (CT) examination in patient triage in the emergency departments, allowing them to be referred to “COVID” or “non-COVID” wards. Initial chest CT examination must be performed without intravenous administration of iodinated contrast material, but contrast material administration is required when pulmonary embolism is suspected, which seems to be frequent in severe forms of the disease. Typical CT features consist of bilateral ground-glass opacities with peripheral, posterior and basal predominance. Lung disease extent on CT correlates with clinical severity. Artificial intelligence could assist radiologists for diagnosis and prognosis evaluation.