However, HIV-infected persons may have compromised ability to react to Ppd-tuberculin skin testing, because HIV infection is associated with an elevated risk for cutaneous anergy.
High risk of active tuberculosis in HIV-infected drug users with cutaneous anergy. JAMA 1992;268:504-9.
A purified protein derivative (PPD) tuberculin skin test may be nonreactive because of cutaneous anergy, technical problems with the test, or absence of tuberculosis infection.
Conditions associated with cutaneous anergy include malnutrition, cachexia, advanced age, metabolic diseases, cancer, infection (especially HIV), drugs, stress, and live-virus vaccinations.(6)
There is ongoing controversy concerning the most reliable method for separating a negative PPD test due to nontuberculous infection from negative tuberculin reactivity secondary to cutaneous anergy. Skin test anergy panels are currently accepted as reasonable tests for determining the patient's ability to respond to delayed-type hypersensitivity (DTH).(5)(7)(8)(9) A patient who fails to respond to any of these antigens is presumed to be anergic.
Only three of the four most reactive antigens (Candida, mumps, and histoplasmin or tetanus) were shown to be necessary in determining cutaneous anergy. As shown in Figure 1, the estimated anergy for the population decreased very rapidly with the addition of the second and third test.
If the PPD test is negative, the question frequently facing the clinician is: is the patient free of tuberculosis infection, or is the PPD test result a false negative secondary to cutaneous anergy? Estimates of nonreactivity to tuberculin in patients with microbiologically proven tuberculosis typically range between 10% and 25%.(10)(11)(12)(13) Our study population showed an anergy rate of 12% after the administration of five control skin test antigens (Figures 1 and 2).