Correlation of immunologic status with high-resolution CT and distributions of pulmonary tuberculosis

Infection in Immunocompromised Hosts: Imaging

Immunocompromised patients are encountered with increasing frequency in clinical practice. In addition to the acquired immunodeficiency syndrome (AIDS), therapy for malignant disease, and immune suppression for solid organ transplants, patients are now rendered immunosuppressed by advances in treatment for a wide variety of autoimmune diseases. The number of possible infecting organisms can be bewildering. Recognition of the type of immune defect and the duration and depth of immunosuppression (particularly in hematopoietic and solid organ transplants) can help generate a differential diagnosis. Radiologic imaging plays an important role in the detection and diagnosis of chest complications occurring in immunocompromised patients; however, chest radiography alone seldom provides adequate sensitivity and specificity. High-resolution computed tomography (CT) can provide better sensitivity and specificity, but even CT findings may be nonspecific findings unless considered in conjunction with the clinical context. Combination of CT pattern, clinical setting, and immunologic status provides the best chance for an accurate diagnosis. In this article, CT findings have been divided into 4 patterns: focal consolidation, nodules/masses, small/micronodules, and diffuse ground-glass attenuation/consolidation. Differential diagnoses are suggested for each pattern, adjusted for both AIDS and non-AIDS immunosuppressed patients.

The impact of glycemic status on radiological manifestations of pulmonary tuberculosis in diabetic patients

Setting

Diabetes mellitus (DM) may increase risk of pulmonary tuberculosis (PTB) and influence its radiological manifestations.

Objective

To evaluate the impact of glycemic status on radiological findings of PTB in diabetic patients.

Methods

Between January 2010 and December 2015, chest radiographs (CXRs) in consecutive 214 DM patients with culture-proved PTB and 123 available thoracic computed tomography (CT) scans were enrolled. An equal number of non-DM patients with similar demographics was included as the control group. Glycemic status was assessed by glycosylated hemoglobin (HbA1c), and a cutoff of 8% was used to further investigate radiological features of diabetic PTB. Two radiologists and one pulmonologist reviewed the chest images independently.

Results

Compared with non-DM patients, primary PTB pattern and extensive disease on CXRs as well as primary PTB pattern, large non-cavitary nodule, more than one cavity in a single lesion, unusual location, and all lobe involvement of lesions on thoracic CT scans were more common in DM patients. Furthermore, diabetics with HbA1c > 8% were more likely to exhibit unusual findings (P < 0.001), far advanced extensive lesions (P < 0.001) on CXRs, lymphadenopathy (P = 0.028), more than one cavity in a single lesion (P < 0.001) and all lobe involvement (P = 0.041) on thoracic CT scans.

Conclusions

Glycemic status influenced radiological manifestations of diabetic PTB. Given an increased risk of atypical radiological presentations of PTB in DM patients, physicians should be alert and pay more attention to those with poor glycemic control.

Utility of high-resolution computed tomography for predicting risk of sputum smear-negative pulmonary tuberculosis

BACKGROUND

To diagnose sputum smear-negative pulmonary tuberculosis (PTB) is difficult and the ability of high-resolution computed tomography (HRCT) for diagnosing PTB has remained unclear in the sputum smear-negative setting. We retrospectively investigated whether or not this imaging modality can predict risk for sputum smear-negative PTB.

METHODS

We used HRCT to examine the findings of 116 patients with suspected PTB despite negative sputum smears for acid-fast bacilli (AFB). We investigated their clinical features and HRCT-findings to predict the risk for PTB by multivariate analysis and a combination of HRCT findings by stepwise regression analysis. We then designed provisional HRCT diagnostic criteria based on these results to rank the risk of PTB and blinded observers assessed the validity and reliability of these criteria.

RESULTS

A positive tuberculin skin test alone among clinical laboratory findings was significantly associated with an increase of risk of PTB. Multivariate regression analysis showed that large nodules, tree-in-bud appearance, lobular consolidation and the main lesion being located in S1, S2, and S6 were significantly associated with an increased risk of PTB. Stepwise regression analysis showed that coexistence of the above 4 factors was most significantly associated with an increase in the risk for PTB. Ranking of the results using our HRCT diagnostic criteria by blinded observers revealed good utility and agreement for predicting PTB risk.

CONCLUSIONS

Even in the sputum smear-negative setting, HRCT can predict the risk of PTB with good reproducibility and can select patients having a high probability of PTB.