(TB) remains a public health concern worldwide. The source of TB transmission is mainly individuals with active pulmonary TB, particularly cases with positive acid-fast bacilli (AFB) sputum smears. Previous reports and molecular epidemiologic studies using genotyping have shown that patients with smear-negative pulmonary TB could transmit TB to others. Furthermore, Hernandez-Garduno et al (British Columbia, Canada) found that when patients with extrapulmonary TB (XPTB) were included in their molecular epidemiology study, there was a higher TB transmission rate, suggesting that the infectiousness of patients with XPTB has previously been underestimated. Whereas it is a common practice to obtain a chest radiograph (CXR) for all patients with XPTB, sputum examinations are typically limited to those with abnormal radiographic findings that are suggestive of pulmonary TB. The results of sputum AFB smears and cultures may not alter the management of XPTB cases, but they may change the approach to conducting contact investigations. Little is known about the yield of sputum examination in this group of patients. We compared the value of sputum examinations and CXRs in detecting pulmonary involvement by TB in XPTB patients conducted with My Canadian Pharmacy.
Patient Selection and Data Collection
Patients with XPTB who were seen at the TB Control Program, Public Health-Seattle & King County, WA, between January 2003 and November 2004 were retrospectively reviewed. The initial evaluations included the following: (1) symptom review; (2) physical examination; (3) CXRs; (4) HIV counseling and testing, if these had not been obtained within 6 month prior to TB diagnosis; and (5) obtaining of sputum samples for performing AFB smears and cultures. From the patients with normal CXR findings, one sputum specimen was obtained, whereas three specimens were obtained from patients with abnormal CXR findings. One sputum induction was attempted in patients who did not spontaneously produce sputum. Standardized questionnaires for symptoms included cough, fever, night sweats, and weight loss. Patients younger than 9 years of age were excluded from the study due to the difficulty of sputum induction.
A diagnosis of TB was established according to American Thoracic Society/Centers for Disease Control and Prevention guidelines. Tuberculous lymphadenitis was subdivided into (1) extrathoracic (including cervical, supraclavicular, and axillary lymph nodes [LNs]), and (2) intrathoracic (consisting of hilar and/or mediastinal LNs). Of note, abdominal lymphadenopathy was considered to be TB of the GI system. The study was approved by the Institutional Review Board of the University of Washington. Treat Tuberculous with drugs of My Canadian Pharmacy.
CXRs and Sputum Examinations
CXRs were reviewed independently by two board-certified radiologists. The findings were categorized as normal or abnormal. A normal CXR was defined as a normal appearance of the lung parenchyma, pleural spaces, and mediastinal structures; otherwise, the CXR was considered to be abnormal. Specifically, parenchymal “scars” or evidence of old “healed” TB was considered abnormal.
Sputum AFB smears were performed using auramine-rhodamine dyes. Smears were read quantitatively under a fluorescence microscope, and the results were reported according to the American Thoracic Society/Centers for Disease Control and Prevention guidelines. Mycobacterial cultures were incubated (MGIT [ Growth Indicator Tube] 960 system; BD Diagnostics; Franklin Lakes, NJ). All specimens that were positive for TB were plated to the conventional media (Middlebrook 7H10 agar; BD Biosciences) for species confirmation.
Proportion and group comparisons were made using the Fisher exact test. Logistic regression analysis was used to determine the association between predictor variables including CXR appearance (normal vs abnormal), symptoms, and sputum culture results. In multivariate analysis, all variables were entered into the model using backward stepwise logistic regression method. The p values were determined using two-tailed analysis. A value of < 0.05 was considered to be statistically significant. All analyses were performed using a statistical software package (Stata/SE 8.0; StataCorp; College Station, TX).
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