Blood Tests More Accurate Than Skin Test in TB Diagnosis

Fewer false positives yielded by blood tests, though results differ between the two

MONDAY, April 24 (HealthDay News) -- Two blood tests, T-SPOT.TB and QuantiFERON-TB Gold, are more accurate in detecting tuberculosis (TB) than the standard tuberculin skin test, according to an article in the April 22 issue of The Lancet.

Luca Richeldi M.D., of the University of Modena and Reggio Emilia in Modena, Italy, and colleagues conducted a prospective study of 393 patients who were suspected of TB infection and were tested simultaneously with T-SPOT.TB and QuantiFERON-TB Gold. Results of a tuberculin skin test were also available for 318 of the patients.

Overall results were similar for the three tests, but the two blood tests produced fewer false positives among those who had received a BCG vaccination. The QuantiFERON-TB Gold test yielded 11 percent indeterminate results, compared with 3 percent for the T-SPOT.TB test. The latter test also produced more positive results -- 38 percent versus 26 percent for the QuantiFERON-TB Gold test.

"There are differences between the two blood assays when they are used in routine practice, especially in the diagnosis of high-risk individuals, such as immunosuppressed patients and young children. The choice of which diagnostic test to use should depend on the population being tested, the purpose of testing and the resources available," the authors conclude.

Richeldi and his institution have in the past received fees from the manufacturers of the two blood tests.

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Jane Parry

Jane Parry

Published on April 24, 2006

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