Effectiveness of a Nosocomial Tuberculosis Control Program at an Urban Teaching Hospital: Discussion
The PPD reactor rate of 12.8% for new employees was quite high compared with a mean initial reactor rate of 1.91% found in the SHEA-CDC survey. This high rate is likely attributable to two facts. First, TB is significantly more prevalent in San Diego than in the nation as a whole. Second, individuals at high risk for TB infection make up a significant number of UCSD’s employees and volunteers. These include foreign-born persons and members of racial and ethnic minorities. It should be noted that the high rate of reactors among new personnel does not contribute to the relatively low conversion rate among established employees seen at our institution. Once an individual has a PPD of 10 mm or more, he or she is not retested. Therefore, these individuals do not appear in the denominator (ie, total PPD tests for established employees) of the skin test conversion rate for established personnel.
In the period from 1993 to 1995, one case of active TB was discovered among the approximately 5,700 employees and volunteers screened at UCSD each year. Careful investigation did not reveal any link to a hospitalized case of TB. It is likely that this employee acquired TB infection in the community.
Of all personnel who were skin-tested after an unprotected exposure to an active case, two convertors were detected (conversion rate, 0.6%). The relatively low conversion rate probably results from several factors. The risk of transmission of TB infection from one individual to another is dependent on the infectiousness of the source case, duration of exposure, proximity of contact, and environmental factors (especially ventilation). It is likely that the TB patients in whom the diagnosis was delayed did not have advanced disease and therefore were not as infectious. Additionally, in many cases the employee exposure was probably very brief compared to a household contact. cialis professional
Compliance with INH therapy among health-care workers is poor. Prior studies have revealed compliance rates ranging from 13% to 66%, with the majority showing rates of 50% or less. Employees and volunteers at UCSD fared no better despite various supportive practices of the TB control program. Improved employee education and possibly even incentives (such as are used to recruit and maintain subjects in clinical trials) might be considered in the future to increase compliance.
In summary, we found a low PPD conversion rate at our institution despite the fact that the medical center cared for a moderate number of patients with TB. The conversion rate was low even when there was known exposure to an active case. Our baseline PPD reactor rate was fairly high, consistent with the relatively high TB case rate in the community and the demographic composition of our employees and volunteers. One case of TB was detected among employees and volunteers at our institution in 3 years. Compliance with INH prophylaxis was poor. These findings suggest that our administrative and engineering controls for prevention of nosocomial transmission of TB are, in general, effective. However, our INH preventive therapy program is ineffective because of poor compliance, and efforts should be directed at improvement in this area.