As discussed by Dr. Barnhart and Ms. Beaudet and as stated in our article [1], the number of respirators used could be reduced through reuse or by restricting access to patient rooms. Unfortunately, these measures will have a limited effect. Respirators cannot be reused indefinitely. Most hospitals cannot afford to have a dedicated caretaker serve meals, clean rooms, give medications, respond to patient requests, and provide baths and examinations. The results of our study, including the number of respirators required per patient-day, were strikingly similar to those reported in a study from the University of Virginia [2].

Dr. Israel correctly states that the mortality rate for tuberculosis will vary according to the presence of comorbid conditions. The mortality rate we chose was the figure used for tuberculosis in developing countries and represents an average rate [3].

More rapid and effective diagnostic tests would be beneficial but are likely to be expensive and thus not routinely used. We examined the standard methods (three sputum samples stained and cultured for acid-fast bacilli).

Dr. Beckett points out that a risk for tuberculosis exists even after patients have been placed in isolation. We discussed the theoretical advantages of the high-efficiency particulate respirator and intentionally used a best-case estimate of its efficacy. Essentially, previous isolation measures (with caretakers using a surgical mask) were assumed to be totally ineffective, and the respirator was assumed to be completely effective. It is unlikely that respirators are this effective.

We were correct in stating that respirators have not been shown to prevent a single case of tuberculosis. No study has documented reduced transmission to health care workers through the use of high-efficiency particulate respirators. Why should we choose this moment to abandon our science? If use of particulate respirators is considered unavoidable, why was there not a system established to measure their efficacy? Barnhart and Beaudet argue that the respirators are highly effective (theoretically) and that rates of tuberculosis in employees are "high," but state that prospective efficacy studies are not feasible because of "sample size" considerations. Given the first two assumptions, an efficacy study should be feasible. We owe it to our patients, employees, and visitors to study the efficacy of prevention measures. Perhaps the most important question is how best to use our limited resources to minimize tuberculosis transmission.