Category Archives: Pulmonary function

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: institution of therapy

For example, it is difficult to quantify the conviction of an alternate diagnosis or the response to nontuberculous therapies from medical notes alone, but these factors may be strongly associated with TB. We evaluated clinical, demographic, and radiographic characteristics that would be easily available early in the diagnostic workup of TB, but may have missed other more subtle determinants that clinicians use that could better predict TB.
The findings of our study can guide clinical practice in settings similar to that of San Francisco General Hospital, a large public hospital in a city that has moderate-to-high levels of TB and HIV prevalence compared to other US cities. It is unclear whether these findings may be generalizable to private hospitals, academic settings with different high-risk groups of patients, and in developing countries. Future studies will need to validate our findings in cohorts of patients in different clinical settings. canadian family pharmacy

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: TST

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: TSTAlthough we were limited to chart review to assess all of the clinical and demographic variables, most of these were routinely assessed in patients in whom TB was suspected. However, we did encounter missing data on an important predictor of smear-negative TB, the TST. We ran our multivariate analysis using the three different techniques outlined in the “Materials and Methods” section and found similar results. The proportion of patients who had documented TST results was significantly different among the study patients and control patients (77% vs 48%, respectively), suggesting a differential suspicion of TB between the two groups of patients. Perhaps the control patients were less likely to have a TST placed because the alternative, more common, diagnosis such as a bacterial pneumonia was responding appropriately to therapy. The study patients may not have responded as well to these therapies, causing the practitioners to pursue the diagnosis of TB more aggressively. canadian neighborhood pharmacy

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: TPS

The TPS was derived using the ^-coefficients of the four multivariate predictors in our study to help clinicians apply our findings. Future studies will need to validate our TPS using a prospective cohort of inpatients. Using the prediction score with a simple cutoff of > 0 to identify persons with TB, we would have missed 12 of 47 study patients (25%) in this study. Using >— 1 as the cutoff point for identifying patients with TB would increase our sensitivity to 94%, but lower the specificity. In the case of any infectious disease with public health implications, it is important to have a test or rule that has a high sensitivity and negative predictive value, so that patients with true disease are treated and those with a low possibility of disease can be discharged from the hospital safely without treatment. However, using an arbitrary cut point to identify patients with TB dichotomizes the TPS and wastes valuable information from each possible result.

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: TB

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: TBOur clinical findings demonstrate that the presence of expectoration in a patient with negative sputum smear results is not associated with TB, a clear distinction from the smear-positive patient. Another more common pulmonary process, such as bacterial pneumonia or bronchitis, is more likely than TB possibly because the major cough receptors in the airways may not be stimulated by the relatively small amount of bacteria in smear-negative disease. This finding supports the results from Senegal, where patients with smear-negative disease had an absence of cough. Similar to smear-positive TB, we found that a positive TST result was highly predictive of TB in smear-negative patients as well. In support of our findings, a recent case-control study that examined predictors of culture-positive TB (regardless of smear status) found a positive purified protein derivative tuberculin test result to be their strongest predictor of TB (OR, 13.2; 95% CI, 4.4 to 40.7). A likely explanation is that the immunologic response to the TST is determined by a much lower burden of TB organisms than what exists even in smear-negative TB.

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: Discussion

To demonstrate the utility of the TPS for clinical decision making, we estimated the probability of TB in a hypothetical patient with negative sputum smear results in three different areas with varying prevalence rates of TB (Table 4). The TPS could affect the posterior likelihood of TB by approximately 30-fold in each of the scenarios described. If the threshold for empiric treatment is 5%, in cities with high TB prevalence, a score of > 0 would predict the risk of TB to exceed the threshold for empiric treatment. In a city with low prevalence of TB, even a positive score would not significantly affect the likelihood that the patient has TB, and withholding treatment pending final culture results for these patients may be prudent.

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: multivariate analysis

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: multivariate analysisIn the multivariate analysis, a positive TST result (OR, 4.8; 95% CI, 2.0 to 11.9) was independently associated with an increased risk of a positive TB culture result, whereas a radiographic pattern not typical of reactivation pulmonary TB (OR, 0.3; 95% CI, 0.1 to 0.7) and expectoration with cough (OR, 0.3; 95% CI, 0.1 to 0.6) were predictive of a decreased risk. We detected an interaction between HIV-positive status and the finding of mediastinal lymphadenopathy on a chest radiograph that was associated with an increased risk of a positive TB culture result as well (OR, 7.2; 95% CI, 1.4 to 36.0; Table 2).
Using the four variables that were associated with the risk of TB in multivariate analysis, we created a TB prediction score (TPS) to help distinguish patients who were culture positive from patients likely to be culture negative. Based on the magnitude of the ^-coefficient, a positive TST result was given a point score of + 1, the negative predictors (expectoration and an infiltrate not typical of TB) received — 1 point each, and HIV positivity and mediastinal lymphadenopathy together received + 2 points.

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: Results

Missing data were managed using three different analytical methods. We ran our logistic regression (1) by excluding subjects who were missing variables necessary to enter the model, (2) by eliminating the variable with the largest amount of missing data, and (3) by creating an indicator variable to represent the missing data. We found that all three techniques yielded similar multivariate results. The results obtained using indicator variables are presented.
Using the ^-coefficients derived from the independent predictors in our logistic regression model, we created a scoring system to clinically apply these predictors. To simplify the predictive model we rounded the ^-coefficient to the nearest integer. We calculated the area under a receiver operating characteristic curve for the prediction rule. We calculated likelihood ratios (LRs) for each potential score. LRs were determined by dividing the proportion of study patients with the score by the proportion of control patients with the score. canadian health&care mall

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: Statistical Analysis

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: Statistical AnalysisWe recorded standard risk factors for TB infection and disease as defined by the American Thoracic Society and Centers for Disease Control and Prevention, including sex, age, ethnicity, country of birth, current or prior homelessness, and current or prior history of incarceration. Clinical information recorded included the presence of cough, expectoration, hemoptysis, temperature > 38.5°C, night sweats, weight loss, symptom chro-nicity, HIV seropositivity, current or prior tuberculin skin test (TST) result, known exposure to TB, prior isoniazid prophylaxis, alcoholism, tobacco use, and other comorbidities associated with TB, such as diabetes, end-stage renal disease, hematologic cancer, or chronic steroid use. The results of the chest radiograph were categorized as normal, upper/apical lobe disease (either infiltrate or cavity), other pattern of infiltration not typically associated with reactivation TB (lobar or diffuse pattern), pleural effusion, mediastinal lymphadenopathy, or miliary pattern. We recorded the number of sputum smears analyzed for each patient as well. The chart reviewer was blinded to the sputum-culture status of the patient. Culture results and initial smear interpretation of each sputum sample were verified.

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results: Materials and Methods

Study Setting and Patients
The study was conducted at San Francisco General Hospital, a university-affiliated public hospital. Patients included in the study were adults admitted to the hospital between 1993 and 1998 with the suspicion of TB, who had at least two negative sputum smear samples and corresponding sputum culture results available. Sputum samples were obtained by spontaneous morning expectoration, saline solution induction, tracheal aspiration, or bronchoscopy with BAL. All sputum smears were concentrated and examined by trained microbiology technicians. Each sputum smear was cultured by both BACTEC 12B broth (Becton-Dickenson; Cockeysville, MD) and Middlebrook 7H11 selective agar and maintained for at least 6 weeks to detect the presence of growing organisms.

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear Results

Identifying Pulmonary Tuberculosis in Patients With Negative Sputum Smear ResultsSince the resurgence of pulmonary tuberculosis (TB) in the United States in the late 1980s, much attention has been focused on early case identification and treatment. Several studies have identified the clinical characteristics of persons with the most infectious form of TB, those harboring the largest number of organisms, with acid-fast bacilli (AFB) found by microscopic examination of stained sputum (AFB smear positive). However, patients with active TB who have negative sputum smear results are also capable of transmitting the infection. The relative transmission rate of smear-negative TB patients compared to smear-positive TB different clinical and radiographic findings than those with smear-positive disease. We are aware of only one previous study from West Africa that identified predictors of smear-negative patients with TB. They found that an absence of cavitation, lack of cough, presence of HIV seropositivity, CD4 cell count > 200/^L, and age > 40 years predicted patients with smear-negative TB.

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