SPUTUM INDUCTION VERSUS FIBEROPTIC BRONCHOSCOPY IN THE DIAGNOSIS OF TUBERCULOSIS

To the Editor :

The article by Conde and colleagues (1) states that sputum induction (SI) is a safe procedure with a high diagnostic yield and a high agreement with results of bronchoscopy for the diagnosis of pulmonary tuberculosis (TB) in patients with and without human immunodeficiency virus (HIV). Although SI and bronchoscopy were both found to be safe for the patients who underwent these procedures, the authors did not discuss the risk of Mycobacterium tuberculosis exposure and transmission to other patients or health-care workers (HCWs) from the procedures or equipment (2, 3).

SI and bronchoscopy are cough-inducing procedures and generate infectious droplet nuclei, causing increased exposure to M. tuberculosis. According to guidelines published by the World Health Organization and the Centers for Disease Control and Prevention, the most important measure for control of TB in health care settings is to reduce exposure of patients and HCWs to infectious droplet nuclei (4, 5). Therefore, cough-inducing and aerosol-generating procedures such as SI and bronchoscopy should not be performed on patients who may have infectious TB unless the procedures are absolutely necessary (4, 5). Although some patients may find it difficult to produce sputum specimens, efforts should still be made to collect at least three noninduced sputum specimens for diagnosis of patients suspected of having pulmonary TB (6). Spontaneous sputum collection may also aerosolize droplet nuclei but can be done outside and away from other people. SI and bronchoscopy require indoor facilities and the close proximity of trained HCWs. When sputum specimens cannot be obtained spontaneously from patients with TB signs and symptoms in regions where TB rates are high, empiric treatment could be considered and may be safer with regard to infection control.

In situations where SI or bronchoscopy are necessary, all efforts should be made to provide appropriate infection control precautions that reduce the exposure of patients and HCWs to M. tuberculosis. Ideally, both procedures should be performed using local exhaust ventilation devices or rooms that meet the ventilation requirements for TB isolation, and those in attendance should wear respiratory protection (5). Environmental controls, such as ventilation devices, may not be available in many resource-limited regions. However, all available measures should be taken to maximize natural ventilation and to control the direction of airflow (4). Although SI and bronchoscopy may be safe for individual patients, without infection control measures, they pose a risk of M. tuberculosis transmission to others.

Centers for Disease Control and Prevention, Atlanta, Georgia

1. Conde MB, Soares SLM, Mello FCQ, Rezende VM, Almeida LL, Reingold AL, Daley CL, Kritski AL. Comparison of sputum induction with fiberoptic bronchoscopy in the diagnosis of tuberculosis. Am J Respir Crit Care Med 2000; 162: 2238-2240 [Abstract/Free Full Text].

2. Hannan MM, Perez H, Maltez F. et al. Investigation and control of a large outbreak of multi-drug resistant tuberculosis at a central Lisbon hospital. J Hosp Infect 2001; 47: 91-97 [Medline].

3. Agerton T, Valway S, Gore B, Pozsik C, Plikaytis B, Woodley C, Onorato I. Transmission of a highly drug-resistant strain (strain w1) of Mycobacterium tuberculosis: community outbreak and nosocomial transmission via a contaminated bronchoscope. JAMA 1997; 278: 1073-1077 [Abstract].

4. World Health Organization. Guidelines for the prevention of tuberculosis in health care facilities in resource-limiting settings. 1999:1-51.

5. Centers for Disease Control and Prevention. Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care facilities, 1994. MMWR 1994;43:RR-13.

6. American Thoracic Society, Centers for Disease Control and Prevention. Diagnostic standards and classification of tuberculosis in adults and children. Am J Respir Crit Care Med 2000;161:1376-1395.

From the Authors:

The letter from Larson and colleagues regarding our article raises an important issue: the risk of Mycobacterium tuberculosis transmission to patients and health-care workers (HCWs) (1). Since 1996, sputum induction (SI) has been performed in the Hospital Universitario Clementino Fraga Filho (HUCFF) inside a special room equipped with a high efficiency particulate air filter (HEPA respirator - model ACCU-U 400, Armor Medical Products, Illinois). In addition, the HCWs responsible for SI have been using personal respiratory protection. None of these HCWs have had a tuberculin skin test (TST) conversion since 1996. Despite the potential risk of transmission of M. tuberculosis in rooms where cough-inducing procedures are performed, it seems that with a well established respiratory control it can be minimized.

In order to minimize the risk of exposure to M. tuberculosis to other patients and HCWs at health care facilities, several steps are required: administrative actions, environmental measures and personal respiratory protection. At our hospital, after the implementation of the Hospital Tuberculosis Control Program (HTCP) in 1998, the rate of TST conversion in HCWs was reduced from 8.2% (1997-1998) to 4.3% (1998-1999) (2). The primary goal of the HTCP has been to identify and isolate patients with respiratory symptoms immediately after admission to the hospital while a smear for acid-fast bacilli is collected and examined.

Another relevant point is that the empirical treatment of pulmonary TB may not be well accepted, even in areas with a high prevalence of TB. At our Hospital, from 1994 to 1996, even among HIV-seronegative patients, 28.5% of TB cases diagnosed empirically actually had another respiratory disease (3). Among HIV seropositive patients, 45.5% of suspected TB cases that were diagnosted empirically were not confirmed subsequently. Thus, significant resources were wasted in the empirical treatment of these patients. Moreover, a case-control study done in the same hospital to evaluate the adverse effects related to anti-TB therapy showed a high rate (6.8%; 40/588) of hepatotoxity, with 85.0% (35/40) of the patients requiring interruption of therapy (4).

According to the World Health Organization (WHO), the best TB control strategy is the prevention of infection through rapid detection and cure of TB patients (5). We believe that SI may be useful for TB control because it is a safe and effective diagnostic tool for the work-up of patients suspected of having active pulmonary TB and who are unable to produce sputum spontaneously. This is true for patients with or without comorbidities, even in places with a high prevalence of TB, like Rio de Janeiro, Brazil.

We agree with Larson and colleagues that cough-inducing procedures, like SI, should be done with appropriate infection control precautions in order to reduce the risk of transmission of M. tuberculosis. As mentioned by Larson and coworkers, in resource-limited regions, measures such as using natural ventilation and controlling the direction of airflow may make it safer to perform SI, but this strategy has not been evaluated under field conditions. In areas of high prevalence of TB, when resources are available, efforts should be made to implement infection control measures to prevent the transmission of M. tuberculosis throughout health care facilities, not only in high risk places.

Hospital Universitario Clementino Fraga Falho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

Arthur Reingold

School of Public Health, University of California, Berkeley, Berkeley, California

Charles L. Daley

Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, San Francisco, California

Afrânio L. Kritski

Hospital Universitario Clementino Fraga Falho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

1. Conde MB, Soares SLM, Mello FCQ, Rezende VM, Almeida LL, Reingold AL, Daley CL, Kritski AL. Comparison of sputum induction with fiberoptic bronchoscopy in the diagnosis of tuberculosis. Am J Respir Crit Care Med 2000; 162: 2238-2240 .

2. Kritski AL, Mello FCQ, Salles CLG, Gonçalves MLC, Anjos Filho L, Pedra A, Loredo C, Curtinhas K, Conde MB et al. The impact of the activities of a Hospital Tuberculosis Control Program. Am J Respir Crit Care Med 2000;161:A 646.

3. Mello FCQ, Soares SLM, Rezende VMC, Conde MB, Kritski L. Brasil empirically treated tuberculosis: clinical profile and results of treatment in AIDS reference center. Rio de Janeiro City. Preliminary results. Int J Tuberc Lung Dis 1996;77(2).

4. Rezende VMC, Conde MB, Soares SLM, Mello FQC, Boabaid R, Imoto FK, Kritski AL. Hepatotoxity in patients submitted to anti-tuberculosis therapy in a hospital reference for acquired immunodeficiency syndrome (AIDS) in Rio de Janeiro, Brazil. Am J Respir Crit Care Med 1999; 159: A552 .

5. World Health Organization. Tuberculosis programme: framework for effective tuberculosis control. Geneva, Switzerland: World Health Organization 1994. Publication WHO/TB/94.179.