Prophylactic group description		PPD (mm)
Persons with known or suspected HIV infection		≥5
Close contacts of person with infectious TB		≥5
Persons with chest radiographic findings suggestive of previous		≥5
	TB and inadequate or no treatment*
Persons who inject drugs and are known to be HIV negative		≥10
Persons with certain medical conditions or factors:		≥10
	Diabetes mellitus, silicosis, prolonged corticosteroid or other immunosuppressive therapy, cancer of the head and neck, hematologic and reticuloendothelial disease (for example, leukemia and Hodgkin's disease), end-stage renal disease, intestinal bypass or gastrectomy, chronic malabsorption syndromes, low body weight (≥10 % below ideal)
Persons in whom PPD converted from negative to positive within the past 2 years		†
Age < 35 years in the following high-prevalence groups:		≥10
	Foreign-born persons from areas of the world where TB is common (for example, Asia, Africa, Caribbean and Latin America)
	Medically underserved, low-income populations including high-risk racial and ethnic groups (for example, Asians and Pacific Islanders, African Americans, Hispanics and American Indians)
	Residents of long-term care facilities (for example, correctional facilities and nursing homes)
	Children younger than 4 years
	Other groups identified locally as having an increased prevalence of TB (for example, migrant farm workers or homeless persons)
Persons < 35 years with no known risk factors for TB		≥15
Occupational exposure to TB (for example, health care workers and staff of nursing homes, drug treatment centers or correctional facilities)		‡
Close contacts with an initial PPD of < 5 mm and normal findings on chest radiography		< 5
	Circumstances suggest a high probability of infection
	Evaluation of other contacts with a similar degree of exposure demonstrates a high prevalence of infection
	Child or adolescent
	Immunosuppressed (for example, HIV infection)