Candida and Tetanus Toxoid Tests
Candida and tetanus toxoid are additional skin tests that can be done to detect delayed-type hypersensitivity. The Candida antigen is a mixture of trichophytin and Oidium. Both antigens are administered in a manner similar to the tuberculin skin test.
Interpretation of absence of normal immune response:
For high-risk patients (HIV infection, intravenous drug abuse, immunocompromise), an induration area larger than 5 mm is considered positive.
For patients at moderate risk (institutionalized patients, healthcare workers), an indurated area larger than 10 mm is significant.
In patients with no significant risk factors, an indurated area of 15 mm or larger is considered positive.
These additional skin tests are helpful in evaluating a negative PPD test in an immunosuppressed person. No reaction to mumps, tetanus, or Candida testing may indicate a false-negative PPD test. However, an induration larger than 2 mm with the mumps, Candida, or tetanus antigen confirms the negative PPD result.