Delay in diagnosing TB and in obtaining drug susceptibility results is believed to have contributed to the number of people whose lives were lost during the TB epidemic the United States experienced between 1985 and 1993.
Current CDC recommendations are that all persons suspected of having pulmonary TB should have a sputum specimen: (a) obtained, (b) cultured, (c) identified, and (d) tested for drug susceptibility. Recent advances in techniques for culturing and identifying M. tuberculosis can shorten the time to final diagnosis from 6-8 weeks to 3-4 weeks. Although these rapid methods exists, 70% of laboratories surveyed in two separate studies reported using non-rapid methods for culturing M. tuberculosis. Approximately 60% of community or hospital-based laboratories and 23% of state laboratories use traditional biochemical testing methods to identify M. tuberculosis. The majority of both types of laboratories use solid media alone--as opposed to radiometric broth methods--for drug susceptibility testing.
Researchers from the Harvard School of Public Health and Brigham and Women's Hospital found that use of currently available rapid diagnostic methods for M. tuberculosis--a combination of solid medium and radiometric broth cultures, nucleic acid probes for identification, and radiometric broth drug-susceptibility testing--substantially decreases the time to diagnosis (from an average 38.5 days to 23 days), time to appropriate therapy (from an average of 6.6 days to 2.0 days), and mortality (22 to 33% lower) in addition to decreasing the average health care costs per patient (9 to 22% lower).
In this era of cost containment, tests with high unit costs may lead to lower overall medical expenditures when diagnostic accuracy and speed are improved. The robustness of rapid diagnostic methods over a range of TB conditions suggests that most laboratories and patients in the United States would benefit from using these methods for the diagnosis of M. tuberculosis.
CONTACT: Beverly Freeman, Harvard School of Public Health Press Office; tel. 617-432-3863; fax 617-432-4710; e-mail <bfreeman@sph.harvard.edu>. Authors: Sally Jody Heymann, MD PhD; Mary Ettling, ScD, Timothy Brewer, MD MPH.
Journal
Public Health Reports