Pulmonary tuberculosis in a high school student and a broad contact investigation: lessons relearned

A case of acid-fast bacillus smear-positive cavitary tuberculosis (TB) was diagnosed in a high school senior (Student A) who lived in a community with a low prevalence for TB. A broad TB investigation was conducted in July 1994 among persons who attended the high school graduation with Student A. Follow-up investigations three months later focused on close contacts at highest risk. A positive tuberculin skin test (TST) was defined as induration of > or = 5 mm after placement of purified protein derivative. We determined the TST results and the estimated costs incurred by the local health department for the broad screening that was conducted. TST results were available for 122/161 (75%) close contacts, and for 1804 persons with nonclose contact with Student A. Her family members were known to have had prior positive TSTs. Positive TSTs were found among 3/122 (2.5%) close contacts, versus 34/1804 (1.9%) persons with nonclose contact. Only one close contact had conversion of TST from negative to positive, and no other active TB case was identified. We estimate the broad TST screening cost the local health department $36,507. Broad TST screening was costly and diverted staff from their customary public health service priorities. Local health departments and clinicians should follow the recommendations of the American Thoracic Society and the Centers for Disease Control and Prevention regarding TB contact investigations.