Table 1. Interpretation of tuberculosis skin test results

A reaction of 5 mm or greater is positive, regardless of age, in the following persons:

  • Persons with known HIV infection
  • Injection drug users whose HIV status is unknown
  • Close contacts of newly diagnosed infectious tuberculosis cases, including health care workers
  • Persons with chest radiographs showing fibrotic lesions

A reaction of 10 mm or greater induration is positive in the following:

  • Foreign-born persons from high-prevalance countries
  • Low-income populations, including high-risk minorities
  • Injection drug users known to be HIV negative
  • Residents of long-term care facilities (for example, nursing homes, correctional institutions)
  • Persons with medical conditions that increase the risk of TB. These conditions include silicosis, diabetes mellitus, prolonged corticosteroid therapy, immunosuppressive therapy, hematologic and reticuloendothelial diseases, end-stage renal disease, intestinal bypass, postgastrectomy, chronic malabsorption syndrome, carcinomas of the oropharynx and upper gastrointestinal tract, and being 10 percent or more below ideal body weight.
Recent tuberculin skin test conversions(within a 2-year period) are considered positive: for those less than 35 years old, a 10 mm or more increase; for those 35 years and older, a 15 mm or more increase.

A tuberculin reaction of 15 mm or more is classified as positive in all other persons.

From: Chapter 7 - Tuberculosis

Cover of Screening for Infectious Diseases Among Substance Abusers
Screening for Infectious Diseases Among Substance Abusers.
Treatment Improvement Protocol (TIP) Series, No. 6.
Center for Substance Abuse Treatment.

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