Author Affiliations: Department of Medicine, Vanderbilt University Medical Center, Nashville, Tenn (Drs Slovis and Haas); and High Point Gastroenterology Associates, High Point, NC (Dr Plitman).
Although anergy testing is commonly used to help interpret negative
tuberculin skin test results, the validity of this approach has not been demonstrated.
Specific issues include lack of a standardized protocol for antigen selection,
number needed to reliably evaluate inability to respond, and uniform criteria
for defining cutaneous reactivity, as well as regional variation in skin test
reactivity. Tuberculin skin testing is used to screen for latent infection
and to evaluate the need for isoniazid prophylaxis. The presence or absence
of reactivity to control antigens does not affect this decision. The results
of anergy testing also do not predict the risk for progression to active disease
in either HIV-negative or HIV-positive patients. In HIV-negative patients
with active tuberculosis, 10% to 20% have negative tuberculin test results,
and 5% to 10% have a negative tuberculin result but have a positive reaction
to another antigen. A negative tuberculin skin test result does not exclude
either latent infection or active disease, even in the presence of a reaction
to other antigens. Neither anergy testing nor tuberculin testing obviates
the need for microbiologic evaluation when there is suspicion for active tuberculosis
infection. Therefore, anergy testing is not useful in screening for asymptomatic
tuberculous infection or for diagnosing active tuberculosis.
Slovis BS, Plitman JD, Haas DW. The Case Against Anergy Testing as a Routine Adjunct to Tuberculin Skin Testing. JAMA. 2000;283(15):2003-2007. doi:10.1001/jama.283.15.2003