Tuberculosis Control Strategies: The Cost of Particulate Respirators

Recent studies showing that tuberculosis can be acquired in the health care setting [1-7] have prompted consideration of environmental control measures to minimize exposure to airborne bacilli. Such measures include private rooms with negative airflow pressure and personal respiratory protection. In October 1993, the Centers for Disease Control and Prevention (CDC) issued draft recommendations for the use of high-efficiency particulate (HEPA) respirators to protect workers from patients who are known or suspected to have tuberculosis [8]. In the same month, the Occupational Safety and Health Administration (OSHA) issued a statement concurring with the use of these respirators. Standard surgical masks are not designed to exclude very small particles and do not provide a tight face-to-mask seal [9, 10]. Particulate respirators fit better and have better filtering capacity than do standard surgical masks. Because particulate respirators are thicker than standard masks, air resistance can make breathing difficult. Therefore, OSHA requires that users be trained and fit-tested to assure an optimal seal between the face and the respirator [11]. This must occur before the respirator is used and must be repeated annually. High-efficiency particulate respirators are expensive, and the training is time-consuming. Unresolved issues include how to deal with workers whose facial hair precludes a tight facial seal. In addition, the efficacy of these respirators is not known. For these reasons, many health care professionals have questioned the choice of the high-efficiency particulate respirators. To characterize the impact and to assess the cost of the mandatory use of the respirators for patients with known or suspected tuberculosis, a questionnaire was given to acute care facilities administered by the Department of Veterans Affairs. Methods In June 1993, a questionnaire was sent to the 159 acute care, inpatient Veterans Affairs facilities in the United States. The questionnaire was addressed to the persons in charge of quality improvement, infection control, and employee health. A second questionnaire was sent to nonresponders, and telephone contact was made as necessary to ensure completion. Acute care facilities were asked about the types of masks or respirators used at their facilities, the number of patients requiring respiratory isolation because of suspected or confirmed tuberculosis each month, and the number of cases of confirmed pulmonary tuberculosis in the past year. Acute care facilities were also asked how many employees converted to a positive protein derivative (PPD) skin test result in the past year and how many developed active tuberculosis in the past 5 years. Facilities estimated the percentage of employees who received annual PPD skin tests by choosing one of five ranges (0% to 20%, 21% to 40%, 41% to 60%, 61% to 80%, or 81% to 100%). The efficacy of the high-efficiency particulate respirators in preventing tuberculosis is unknown. Tuberculosis may result from community-based exposure or may occur in the health care setting when tuberculosis is not identified promptly and contagious patients are not isolated at admission [12, 13]. Transmission may also occur when contaminated air is exhausted into patient care areas [7, 8]. In each of these cases, particulate respirators would not be used and therefore could not prevent disease. For analysis, it was assumed that half of the cases of tuberculosis in health care workers were acquired in health care settings [14] and that half of exposures in health care settings occurred before patients were effectively isolated [12, 13]. Thus, as many as 25% of exposures would occur after isolation when particulate respirators would be used. Therefore, to simulate a best-case scenario, we assumed that the high-efficiency particulate respirators would prevent 25% of all employee exposures to tuberculosis. The mortality rate for tuberculosis in health care workers is unknown but was estimated to be 7% based on the annual incidence of disease and the annual death rate from tuberculosis [15, 16]. A 1-month study of patients in the Iowa City Veteran Affairs Medical Center and at the University of Iowa Hospitals and Clinics showed that an average of 20 masks per 8-hour shift were used for patients in respiratory isolation. The average duration of isolation per patient was assumed to be 14 days for patients with confirmed tuberculosis and 5 days for uninfected patients who were isolated while test results were pending. Standard surgical cup masks cost $0.10 each, whereas the dust-mist, dust-mist-fume, and high-efficiency particulate respirators cost $0.62, $2.75, and $4.10, respectively. Results Questionnaire All 159 facilities returned the questionnaire (100% response). Seventy-nine facilities (50%) already used particulate respirators, 40 used dust-mist respirators, 38 used dust-mist-fume respirators, and 1 used high-efficiency particulate respirators. One hundred fifty-one facilities (95%) provided data on the numbers of patients in isolation. In these facilities, 1063 patients were reported to be isolated each month for known or suspected tuberculosis. If facilities that did not respond to the question are assumed to have results similar to those of responders, approximately 1119 patients would be estimated to be in isolation for known or suspected tuberculosis every month in the Veterans Affairs system. When the data were analyzed by facility, the median number of patients isolated was 3 per month per facility (range, 0 to 60) (Table 1). Table 1. Results of Questionnaire The median number of patients with confirmed pulmonary tuberculosis in the last year was 3 per facility (range, 0 to 68) (Table 1). The number of employees who developed active tuberculosis in the past 5 years ranged from 0 to 4 per facility. Fifty-four cases of tuberculosis in employees were identified; 117 (75%) of the 155 responders reported no known cases of tuberculosis in employees. If facilities that did not respond to the question are assumed to have results similar to those of the responders, approximately 11 cases would be expected each year. One hundred forty-one facilities provided data on PPD test conversions by employees within the past year. The results ranged from 0 to 75, with a median of 2, but this number may not be a reliable estimate for several reasons. Written comments indicated that some facilities were unable to separate employees who had not received a PPD test in several years. Employees with known exposures outside the health care setting were included. Some hospitals included positive PPD test results found during physical examinations done before employment. In addition, most hospitals did not actually provide annual skin tests to all employees. Thirty-three (23%) of the 141 facilities reported no skin-test conversions in employees. One hundred forty-nine facilities provided estimates of the proportion of employees who received annual PPD tests (Figure 1). Written comments indicated that many hospitals in the lower range were aware of the problem and were instituting new programs to improve compliance. Figure 1. Percentage of employees receiving annual purified protein derivative skin tests at each facility (149 facilities providing data). Cost of Particulate Respirators Used during Patient Care Compared with the use of the standard cup surgical mask, use of the high-efficiency particulate respirator in the Veterans Affairs system would result in excess costs of $19 million annually. Compared with the use of dust-mist or dust-mist-fume respirators, use of the high-efficiency particulate respirators would result in annual excess costs of $16 million and $6 million, respectively. Assuming that 25% of cases of pulmonary tuberculosis in employees could be prevented by the high-efficiency particulate respirators, their use would result in an excess cost of $6.6 million per case of pulmonary tuberculosis prevented compared with the standard surgical cup mask. Tuberculosis in employees may be under-reported because employees may seek care outside of the Veterans Affairs system. If the rate of tuberculosis in physicians, housestaff, and nurses was twice that of the general population [17, 18], 14.5 cases of pulmonary tuberculosis would be expected each year, and the excess cost per case prevented by the high-efficiency particulate respirators would be $5.1 million. Using these figures, these respirators would result in excess costs of $72 to $95 million per life saved. Other Costs Use of these respirators also requires fit-testing and training of all health care workers involved in treating patients suspected of having tuberculosis. The Veterans Affairs system currently employs 13 967 physicians, 14 589 residents, and 40 699 nurses [17]. If no other staff were trained and if one high-efficiency particulate respirator was used for each person who had fit-testing, $283 946 would be spent annually for respirators used for training ($102 000 per case of tuberculosis prevented and $1.5 million per life saved) (Table 2). The time lost from work was calculated using the average salary for physicians, nurses, and residents, assuming that training and fit-testing would require 30 minutes per person. Training and fit-testing would annually cost $678 000 in time lost from work. Table 2. Excess Costs Resulting from Using High-Efficiency Particulate Respirators Compared with Surgical Cup Masks Adding these costs to the cost of respirators used in patient care settings, the excess cost per case of tuberculosis prevented would be approximately $7 million, and the excess cost per life saved would be $100 million (Table 2). National Estimates Using the above estimates and assuming that 26 000 cases of pulmonary tuberculosis occur per year [18], an excess of $462 million would be spent annually on high-efficiency particulate respirators used for patient care alone. The cost of training and fit-testi