Lung deposition of inhaled drugs increases with age?

Adjunctive tests for diagnosis of tuberculosis: serology, ELISPOT for site-specific lymphocytes, urinary lipoarabinomannan, string test, and fine needle aspiration

The diagnostic gold standard for active tuberculosis (TB) is the detection of Mycobacterium tuberculosis (MTB) by culture or molecular methods. However, despite its limited sensitivity, sputum smear microscopy is still the mainstay of TB diagnosis in resource-limited settings. Consequently, diagnosis of smear-negative pulmonary and extrapulmonary TB remains challenging in such settings. A number of novel or alternative techniques could provide adjunctive diagnostic use in the context of difficult-to-diagnose TB. These may be especially useful in certain patient groups such as persons infected with human immunodeficiency virus (HIV) and children, who are disproportionably affected by smear-negative and extrapulmonary disease and who are also most adversely affected by delays in TB diagnosis and treatment. We review a selection of these methods that are independent of nucleic acid amplification techniques and could largely be implemented in resource-limited settings in current or adapted versions. Specifically, we discuss the diagnostic use and potential of serologic tests based on detection of antibodies to MTB antigens; interferon gamma release assays using site-specific lymphocytes; detection of lipoarabinomannan, a glycolipid of MTB, in urine; the string test, a novel technique to retrieve lower respiratory tract samples; and fine needle aspiration biopsy of lymph nodes.

Prospective study of sputum induction, gastric washing, and bronchoalveolar lavage for the diagnosis of pulmonary tuberculosis in patients who are unable to expectorate

BACKGROUND

Many adults with pulmonary tuberculosis are unable to expectorate. Gastric washing, sputum induction using nebulized hypertonic saline, and bronchoscopy with bronchoalveolar lavage have all been used to obtain specimens for diagnosis, but to our knowledge, the timing and volume of induced sputum have not been well studied, and these 3 methods have not been compared.

METHODS

The study recruited consecutive adult inpatients with chest radiography findings suggestive of tuberculosis who were unable to expectorate. Subjects provided 3 induced sputum samples for culture on day 1 and additional samples on days 2 and 3. In addition, gastric washing specimens were collected on days 1, 2, and 3. A proportion of subjects with negative smear results underwent bronchoalveolar lavage.

RESULTS

The study recruited 140 subjects. Among 107 subjects who provided 3 gastric washing specimens and at least 3 induced sputum specimens, 43% had cultures positive for Mycobacterium tuberculosis. Use of 3 induced sputum samples detected more cases than did use of 3 gastric washings (39% vs. 30%; P=.03). Among 79 subjects with culture results for all 5 induced sputum specimens, there was no difference in yield between samples obtained by induced sputum induction performed in a single day or that performed over 3 days (34% vs. 37%; P=.63). There was no association between sputum volume and positive culture results. No additional cases were diagnosed in the 21 patients who underwent bronchoscopy.

CONCLUSIONS

Use of 3 induced sputum samples was more sensitive than use of 3 gastric washings for diagnosis of tuberculosis in patients who could not expectorate spontaneously. Use of bronchoscopy with bronchoalveolar lavage did not increase diagnostic sensitivity. Samples could be collected in 1 day, allowing for faster diagnosis, faster initiation of treatment, and shorter hospital stay.