Correspondence
HEPA Respirators and Tuberculosis in Hospital Workers
N Engl J Med 1994; 331:1658-1660December 15, 1994
- Article
To the Editor:
Adal et al. (July 21 issue)1 demonstrate that at the University of Virginia Hospital, where the incidence of tuberculosis is low, the infection controls already instituted may be sufficient and the cost of adding respirators with high-efficiency particulate air filters (HEPA respirators) for their 3852 workers is impressively high. The situation is different at our hospital, Lincoln Medical and Mental Health Center in South Bronx, New York. In contrast to their figure of 11 patients with documented tuberculosis per year, we have over 160 such patients per year, of whom approximately 30 percent have multidrug-resistant tuberculosis. As a result, in about 160 of our employees the purified-protein-derivative (PPD) skin test became positive during 1992 and 1993, requiring expensive prophylactic treatment.
At the University of Virginia Hospital there is probably no more than one patient with suspected tuberculosis on a given floor, whereas we have an entire floor of such patients. At our hospital, it is unlikely that patients on the tuberculosis ward will have the benefit of 50 visits by hospital workers per day. Rather, we estimate that the number of visits ranges from 10 to 15 per day. All patients are seen by the same dedicated medical and nursing staff on the same medical round, and only one mask is used per employee per medical round. We estimate that about 50 to 100 workers are exposed to tuberculosis each day. If each one uses one mask per day, the yearly cost could be less than $400,000. Since the rate of PPD conversion is so high, the costs of annual examinations are unavoidable at our institution and should not be added to the cost of HEPA respirators.
Policy makers should not use the inflated costs reported by Adal et al. to cut the budget for new protective measures. The war against tuberculosis is far from over, and we have a lot to lose in this battle.
1 ReferencesEitan Sobel, M.D.
Lincoln Medical and Mental Health Center, Bronx, NY 105411
Adal KA ,Anglim AM ,Palumbo CL ,Titus MG ,Coyner BJ ,Farr BM . The use of high-efficiency particulate air-filter respirators to protect hospital workers from tuberculosis -- a cost-effective analysis. N Engl J Med 1994;331:169-173
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To the Editor:
At our 800-bed university-associated hospital in Winston-Salem, North Carolina, patients with tuberculosis are isolated in rooms with negative-pressure, 100 percent external exhaust, and workers entering these rooms wear midgrade surgical masks whose fit has not been tested. During the past academic year (July 1993 to June 1994), we had 14 cases of tuberculosis, and the PPD-conversion rate was 0.1 percent among our workers (5 of 3806). All five workers with conversion to a positive PPD skin test were evaluated for exposures to any of the 14 patients with tuberculosis; none were documented. During the previous four years, all exposures of personnel to patients with tuberculosis have been evaluated by the PPD skin test; no conversions have occurred. Thus, at our institution the figures provided by Adal et al. would underestimate the cost of preventing a single case of occupationally acquired tuberculosis.
Robert J. Sherertz, M.D.
Bowman Gray School of Medicine of Wake Forest UniversityStephen A. Streed, M.S.
North Carolina Baptist Hospitals, Winston-Salem, NC 27157To the Editor:
Adal et al. calculate that it would cost $1.3 million to $18.5 million to prevent one case of tuberculosis in workers at their hospital through the use of HEPA respirators. The use of HEPA respirators is recommended by the draft guidelines of the Centers for Disease Control and Prevention (CDC)1 and required by the Occupational Safety and Health Administration.2 These respirators have a high filter efficiency for mycobacterial aerosols (>99.99 percent),3 and with proper fitting should have less leakage around the face seal than the submicron surgical mask.
As part of a pilot program our hospital personnel underwent a 45-minute training session in the proper use of HEPA respirators conducted by an industrial hygienist and an infection-control clinician. All subjects passed the initial fit test with the 3M HEPA respirator (model 9970) and the irritant-fume qualitative fit test. Twelve employees were later retested after using these masks during clinical activities (mean, 4.8 uses), and four (33 percent) failed the irritant-fume fit test because of leakage around the face seal. Five employees were retested a second time after additional use of their respirators, and two of them again failed the test.
We conclude that despite intensive training a substantial number of employees fail follow-up fit tests. These results may have been due to the deformation of the mask during use or to employees' failure to adjust the mask properly for a tight seal. Any leakage around the face seal will nullify the slight advantage offered by HEPA respirators.
If additional studies find that face-seal leakage of HEPA respirators is common despite intensive training of workers, then the use of these expensive respirators will not be of even theoretical benefit in preventing tuberculosis in health care workers.
3 ReferencesVickie Brown, R.N.
Carolyn Bishop, M.S.P.H.
William A. Rutala, Ph.D., M.P.H.
David J. Weber, M.D., M.P.H.
University of North Carolina Hospitals, Chapel Hill, NC 275141
Department of Health and Human Services, Centers for Disease Control and Prevention
Medline2
Enforcement policy and procedures for occupational exposure to tuberculosis. Occupational Safety and Health Administration Enforcement document. Washington, D.C.: Department of Labor, October 8, 1993.
3
Chen S-K ,Vesley D ,Brosseau LM ,Vincent JH . Evaluation of single-use masks and respirators for protection of health care workers against mycobacterial aerosols. Am J Infect Control 1994;22:65-74
CrossRef | Web of Science | Medline
Author/Editor Response
The authors reply:
To the Editor: Dr. Sobel indicates that his tuberculosis ward has a high rate of conversion of the PPD test and suggests that the use of HEPA respirators will prevent this, but there are no epidemiologic data demonstrating the effectiveness of HEPA respirators. The CDC has reported successful control of outbreaks of multidrug-resistant tuberculosis in New York hospitals without the use of HEPA respirators.1 We recently surveyed resident physicians in internal medicine at the University of Virginia who had worked at an affiliated tuberculosis hospital that used negative-pressure ventilation, ultraviolet lights, and simple isolation masks for protection. Fifty-two responding physicians did 70 six-week rotations on tuberculosis wards without a single conversion (95 percent confidence interval, 0 to 1 conversion every 8 physician-years). These data suggest that transmission is unlikely with the use of simple isolation masks in tuberculosis wards if conventional administrative and engineering controls are used correctly.2 Similar results have been reported by the tuberculosis service at the National Jewish Center for Respiratory Health and Immunology.
We agree with Dr. Sherertz and Mr. Streed that our cost analysis probably underestimated the average cost of preventing a single case of occupationally acquired tuberculosis. After carefully analyzing the rate of conversions over an additional 12-month period, we have revised our calculations to incorporate the assumption that HEPA respirators may be able to prevent one PPD conversion every 24 months. Thus, it would take a minimum of 82 years on average to prevent a single case of tuberculosis at our hospital at a cost of $2.6 million to $36.9 million for HEPA respirators and medical evaluation, training, and fit testing before their use.
We agree with Ms. Brown and colleagues that the proposed requirement for fit testing of HEPA respirators should be scientifically validated, preferably before a policy decision is made. Others have reported problems with the reliability of fit-testing results.3
Until data from additional epidemiologic studies are available, we advocate the use of dust-mist respirators, which have been used successfully with conventional administrative and engineering measures to control epidemics of multidrug-resistant tuberculosis in New York and have a filtering efficiency of 98 percent for mycobacteria.4 Health care workers can be instructed to apply these masks tightly to the face without special training sessions. Medical evaluation appears unnecessary for dust-mist respirators because of their similarity to simple isolation masks.
4 ReferencesKarim A. Adal, M.D., M.S.
Anne M. Anglim, M.D., M.S.
Barry M. Farr, M.D., M.Sc.
University of Virginia Health Sciences Center, Charlottesville, VA 229081
Maloney S, Pearson M, Gordon M, Castillo RD, Boyle J, Jarvis W. Nosocomial multi-drug resistant tuberculosis revisited: assessing the efficacy of recommended control measures in preventing transmission to patients and health care workers. Ann Intern Med (in press).
2
Jernigan JA, Adal KA, Anglim AM, Byers KE, Farr BM. Mycobacterium tuberculosis transmission rates in a sanitarium: implications for new preventive guidelines. Am J Infect Control (in press).
3
Segal-Maurer S ,Kalkut GE . Environmental control of tuberculosis: continuing controversy. Clin Infect Dis 1994;19:299-308
CrossRef | Web of Science | Medline4
Chen S-K ,Vesley D ,Brosseau LM ,Vincent JH . Evaluation of single-use masks and respirators for protection of health care workers against mycobacterial aerosols. Am J Infect Control 1994;22:65-74
CrossRef | Web of Science | Medline
