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AIDS Treatment News
Tuberculosis Control: Many Cases Found Transmitted
John S. James
February 18, 1999
AIDS TREATMENT NEWS Issue #313, February 18, 1999

The standard test for infectious tuberculosis, the acid-fast bacilli (or AFB) smear, fails to detect many people who are in fact infectious, new research has shown.(1) At least one sixth of TB patients diagnosed in San Francisco since 1991 acquired the infection from persons who were not detected as infectious by the standard test. This was determined by analysis of a database of "DNA fingerprinting" of the TB bacteria from over 1,300 patients. The research was supported by the U.S. National Institutes of Health, and the McLaughlin Foundation of Canada The findings "suggest that while the use of the sputum smear does identify the most infectious patients, those with negative smears should not be considered non-infectious, particularly to highly susceptible people such as those infected with HIV," said Peter M. Small, M.D., one of the researchers, who is Assistant Professor of Medicine at Stanford Medical Center. The AFB smear is still useful because it detects those who are most infectious. This new information could improve tuberculosis control around the world, if it is applied. A major problem is that more sensitive tests, such as sputum cultures, are usually too expensive for use in developing countries. The researchers said that it is imperative that a more sensitive but affordable test be developed quickly. "It is a travesty that in most parts of the world, a disease which kills three million people a year is still diagnosed with a 100-year-old test," said Dr. Small. References 1. Behr MA, Warren SA, Salamon H, and others. Transmission of Mycobacterium tuberculosis from Patients Smear-Negative for Acid-Fast Bacilli. THE LANCET February 6, 1999; volume 353, pages 444-449. (Also see editorial in the same issue, Interpretation of Cluster Studies of Tuberculosis, pages 427- 428.)