Table 3.

Target for tuberculin skin testing and who should be considered for treatment.

Tuberculin skin test reaction size, (mm induration)	Situation in which reaction is considered positive
TST≥5 mm	HIV seropositive
	Close contact with positive AFB in the sputum
	Fibrotic changes on chest radiograph consistent with prior untreated tuberculosis
	Organ transplants and other immunosuppressed patients (e.g., persons receiving the equivalent of 15 mg/day of prednisone for at least 30 days or more)
TST≥10 mm	Injection drug use
	Residents and employees in high-risk settings: nursing homes, and other long-term care facilities, hospitals
	Persons at increased risk of developing active tuberculosis: those with silicosis, diabetes mellitus, chronic renal failure, leukemia, lymphoma, cancer of the head, neck or lung, weight loss of more than 10% of ideal body weight, gastrectomy, jejunoileal bypass
	Children younger than four years of age
TST≥15 mm	Persons with no risk factors for tuberculosis
Contraindications for treatment	Any clinical, radiological, or bacteriological evidence of TB disease