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Proportion of TB cases attributable to extrapulmonary TB may be increasing
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The proportion of tuberculosis cases that are extrapulmonary may have increased by approximately 5% over a 13-year period, according to results of a recent study.
CDC researchers examined data that were submitted by all 50 states between 1993 and 2006 to the National TB Surveillance System. It was determined that the epidemiology and risk factors for extrapulmonary and pulmonary TB may differ.
There were 253,299 cases of TB reported in the United States during the study years. Pulmonary TB was reported in 73.6% of cases. Extrapulmonary TB was reported in 18.7% of cases. The breakdown of extrapulmonary TB cases was as follows:
- lymphatic (40.4%)
- pleural (19.8%)
- bone and/or joint (11.3%)
- genitourinary (6.5%)
- meningeal (5.4%)
- peritoneal (4.9%)
- unclassified extrapulmonary TB (11.8%)
In comparison with pulmonary TB, extrapulmonary TB was positively linked to female gender and birth in a foreign country. The OR for HIV status among patients with extrapulmonary TB compared with patients with pulmonary TB was 1.1.
Compared with pulmonary TB, extrapulmonary TB had negative associations with multidrug resistance, homelessness and excess alcohol use.
There were slower decreases observed in annual case counts for extrapulmonary TB compared with pulmonary TB. In 1993, extrapulmonary TB accounted for 15.7% of TB cases. By 2006, that number had risen to 21%.
Peto H et al. Clin Infect Dis. 2009;49:1350-1357.