Table 3.

Interpretation of TST based on CDC guidelines.

TST reaction size (mm)	Reaction is considered positive
≥ 5	HIV infected individuals
	Recent contact with active TB patients
TB signs on X-ray such as fibrotic changes
organ transplant patients & immunosuppressed individuals
≥ 10	Immigrants from endemic/high prevalence countries in the last 5 years
	Injection drug abusers
	High-risk congregate settings (e.g., nursing homes, homeless shelters, or prisons, Mycobacteriology laboratory workers)
Chronic medical conditions that increase the risk for TB
Children younger than 5 years of age
≥ 15	People with no known risk factors for TB
TST reaction size (mm)	Reaction is considered negative
0 or <5, 10, 15	No induration or a measurement below the defined cut point for each category