Deliberations about Unexpected Pulmonary Involvement in Extrapulmonary Tuberculosis Patients

pulmonary involvementThis study described the CXR findings of 72 XPTB patients and sputum examinations of 57 XPTB patients. The main objective was to assess the value of CXRs and sputum examinations for the identification of XPTB patients with pulmonary involvement, especially those with unrecognized disease, who could be potentially infectious. A few other analyses of the study were performed (1) to find predictors of culture-positive sputum among XPTB cases and (2) to examine whether collecting sputum increases the possibility of culture confirmation.

Patient characteristics of XPTB in our study were similar to those of previous reports in that female patients were affected more often than male patients, and no age-group predilection was observed. Fifty-nine of 72 XPTB patients (82%) were foreign born. In this study, Asians were the predominant racial group (44%), which differs from other reports in which blacks and Hispanics have been more commonly reported. This ethnoracial disparity, at least in part, reflects the racial-ethnic distribution of TB cases in King County, WA (26% black, 8% Hispanic, and 44% Asian during the study period). As in earlier reports,’’’ the most frequent sites of disease were the LNs and pleura. Five of 57 patients (9%) with available HIV test results were infected with HIV.

Interestingly, 2 of 24 XPTB patients (8%) with normal CXR findings and negative HIV status had a positive sputum culture result. This raises public health concerns about the common clinical practice of foregoing sputum collection in such patients. Those two XPTB patients with positive sputum culture results and normal CXR findings had negative sputum AFB smear results. Our results suggest that CXRs do not capture all XPTB patients with pulmonary involvement. Some studies, have reported that approximately 10% of pulmonary TB patients with positive sputum culture results could have normal CXR findings, although those studies included HIV-infected individuals. Our findings, showing that 5 of 12 XPTB patients (42%) whose sputum specimens yielded positive culture results had normal CXR findings, further underscore the limitations of CXR findings in the setting of XPTB. Treat infections with drugs of My Canadian Pharmacy.

Factors that predict the likely transmission of TB include AFB sputum examination and radiographic AFBfindings. Guidelines on contact investigation state that “patients who have lung cavities observed on a CXR typically are more infectious than patients with noncavitary pulmonary disease.” Although it is reasonably assumed that patients with normal CXR findings are even less infectious, they may be infectious when sputum culture results are positive, particularly prior to the initiation of effective therapy. The transmission of TB from smear-negative, culture-positive patients has been well documented in other settings. Clinical epidemiologic studies- have shown that TB transmission occurs from smear-negative pulmonary TB patients, although the likelihood is lower than the transmission from smear-positive pulmonary TB cases. Some molecular epidemiologic studies have further confirmed this notion. Behr and colleagues in San Francisco reported that at least 17% of TB cases were transmitted by smear-negative individuals. Similar findings were observed in the study from British Columbia, Canada, by Hernandez-Garduno et al. Behr et al excluded any XPTB cases, but Hernandez-Garduno et al included XPTB cases, which constituted 29.7% of all TB cases, and suggested that the infectiousness of XPTB patients has been underestimated.

Of all clinical manifestations, our analysis suggests that weight loss is a risk factor for positive sputum culture results in XPTB patients. If sputum had been collected only when a patient had a history of weight loss, it would have led to the collection of sputum in 12 of 72 XPTB patients (17%), resulting in the detection of 7 of the 12 patients (58%) with positive sputum culture results.

The potential clinical value of obtaining a positive sputum culture result from XPTB patients, in addition to the importance of the public health aspect, includes the opportunity to obtain drug susceptibility results. Indeed, one of the XPTB patients in this series had a positive culture result from a sputum specimen, but not from any other specimens, which permitted susceptibility testing and geno-typing. As XPTB tends to be a paucibacillary disease and it may be difficult to obtain positive culture results from an extrapulmonary site, the collection of sputum might be useful in some settings.

Our study has a few limitations. First, a small sample size did not allow us to draw a robust conclusion on the necessity of a sputum examination. A larger study is required to verify our findings and to strengthen the power to identify risk factors for positive sputum culture results in patients with XPTB. Second, we collected only one sputum specimen from the patients with normal CXR findings due to resource consideration. If we had obtained three specimens, it might have increased the detection of unrecognized pulmonary involvement. Last, further investigation is warranted to determine whether recovering TB from the sputum of XPTB patients with normal CXR and positive sputum culture findings can lead to an interruption in the transmission of or an increase in the detection and treatment of recently acquired latent TB infection defeated by remedies of My Canadian Pharmacy.

In summary, although it is not routine practice to perform AFB sputum examination in otherwise immunocompetent XPTB patients with normal chest imaging results, sputum examination may nonetheless identify subclinical involvement of the respiratory system with TB. The potential for TB transmission in this scenario and the implications for TB control remain to be elucidated.

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