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Purpose: The mortality rate form inhalational anthrax during the U.S. 2001 attack was significantly lower than had been observed historically. Current multi-drug therapy and intensive care may have improved survival. Our goal was to systematically evaluate the predictors of disease progression and mortality on which to base treatment recommendations and to compare recent cases to historical controls.
Methods: We searched MEDLINE from 1964 to November 2003 and the bibliographies of all retrieved articles for case reports of inhalational anthrax presenting between 1900 and 2003. We considered articles in any language eligible for inclusion if the authors established a definitive diagnosis of inhalational anthrax. We estimated mortality as a function of duration between symptom onset and antibiotic initiation using a Weibull model of disease progression and observed mortality rates. We used a logistic regression and Kaplan-Meier curves to evaluate the effects of patient characteristics and alternative treatment regimens on mortality and disease progression.
Results: We found 73 reports of 60 cases of inhalational anthrax presenting between 1900 and 2001. Mortality was not significantly associated with the type of therapy given (e.g. single or multi-drug regimens or anthrax anti-serum), but was significantly reduced among U.S. 2001 cases (OR 0.05; 95% CI: 0.004-0.6) and those patients who had antibiotics or serum initiated during the prodromal phase of disease (OR 0.05; 95% CI: 0.008-0.3). Advancing age significantly increased the observed mortality (OR 1.08; 95%CI: 1.01-1.15). Analyzing all cases, the untreated prodromal phase mean duration (4.2 days) was longer than historical accounts. This duration was not significantly affected by type of anthrax exposure (e.g. occupational verses bioterrorism) or when therapy was initiated. Patients who progressed to the fulminant phase had a mortality rate of 96% (regardless of the treatment they received). Most surviving patients (10/13) had pleural effusions requiring drainage. The observed mean time from symptom onset to antibiotic initiation during the U.S. 2001 attack was 3.9 days. Initiation of antibiotics on day two rather than day four reduces mortality by an estimated 56%.
Conclusions: Rapid initiation of antibiotics or anti-serum during the prodromal phase of inhalational anthrax dramatically reduces mortality. Despites advances in supportive care, fulminant phase inhalational anthrax is usually fatal. Efforts to improve early diagnosis and timely initiation of appropriate antibiotics are critical in reducing mortality.
See more of Poster Session - Public Health; Methodological Advances
See more of The 26th Annual Meeting of the Society for Medical Decision Making (October 17-20, 2004)