Skin test reactions to Mycobacterium tuberculosis purified protein derivative and Mycobacterium avium sensitin among health care workers and medical students in the United States

Int J Tuberc Lung Dis. 2001 Dec;5(12):1122-8.


Setting: Health care workers and medical students in the United States subject to annual tuberculin skin testing.

Objective: To use skin testing with Mycobacterium avium sensitin (MAS) to determine contemporary rates of infection with non-tuberculous mycobacteria (NTM) and their effect on reactions to M. tuberculosis purified protein derivative (PPD).

Design: Dual skin testing was performed with PPD and MAS on 784 health care workers and medical students in the northern and southern US. MAS reactions that were > or = 5 mm and also > or = 3 mm larger than the PPD reaction were defined as MAS dominant and due to NTM.

Results: MAS reactions were > or = 5 mm in 40% and > or = 15 mm in 18% of subjects; 95% were MAS dominant. MAS dominant reactions were more common in the south than the north (P < 0.001). PPD reactions were > or = 15 mm in 3% of subjects. PPD reactions > or = 15 mm were more common among males, foreign born subjects and subjects with BCG immunization (all P < 0.001). MAS dominant reactions were found in 82% of subjects with 5-9 mm PPD reactions and 50% with 10-14 mm PPD reactions; these reactions were more common among whites (P = 0.046), US-born (P = 0.038) and subjects without BCG immunization (P = 0.004).

Conclusions: Infections with NTM are responsible for the majority of 5-14 mm PPD reactions among US-born health care workers and medical students subject to annual tuberculin testing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Antigens*
  • Female
  • Health Personnel / statistics & numerical data*
  • Humans
  • Male
  • Middle Aged
  • Mycobacterium avium Complex / immunology*
  • Mycobacterium tuberculosis / immunology*
  • Prevalence
  • Reference Values
  • Students, Medical / statistics & numerical data*
  • Tuberculin Test* / methods
  • Tuberculin*
  • Tuberculosis / diagnosis*
  • Tuberculosis / epidemiology*
  • Tuberculosis / immunology
  • United States / epidemiology


  • Antigens
  • Tuberculin
  • sensitin