Tuberculosis surveillance: lessons from a cluster of skin test conversions.

Mycobacterium tuberculosis has reemerged as a significant public health problem. Elderly persons, especially those in long-term care facilities, are among those at high risk for infection with M. tuberculosis. Frequently, their symptoms are not clearly indicative of M. tuberculosis, and the diagnosis may thus be missed. We discuss the investigation of a cluster of skin test conversions on one locked unit in our long-term care facility. During the epidemiologic investigation, four of 25 patients who had previously had negative results of purified protein derivative testing (16%) and eight of 95 employees (11%) had skin test conversions. Despite a comprehensive, costly evaluation, the index case was not found. We identified weaknesses in our employee and patient M. tuberculosis surveillance programs. Employee baseline purified protein derivative testing data were inadequate. Annual skin tests for employees with previously negative results were not mandatory. There was no mechanism in place to encourage compliance. We developed a plan to educate personnel about the reemergence of M. tuberculosis, signs and symptoms in elderly patients, and the placement and interpretation of purified protein derivative skin tests. Documentation of purified protein derivative surveillance of both patients and employees was computerized. The number of inpatient and outpatient negative-pressure rooms was increased. Appropriate personal protective equipment was made available for use in high-risk situations.