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Dr. Mancuso and his colleagues conducted outbreak investigations in deployed locations such as the Balkans and Afghanistan, where they collected and reviewed medical records of reported active and latent TB cases in deployed U.S. Army service members. They then obtained the medical histories of these soldiers, including prior diagnoses and treatments, determined current symptoms and interviewed the subjects to identify other possible risk factors. Finally, they retested all available skin test converters.

Repeat testing of converters (positives) found that 30 to 100 percent were negative on retesting, wrote Dr. Mancuso. In one case, 95 percent of positive TB tests (38 of 40 tests) from Army National Guard servicemen in Kosovo were subsequently found to be negative, and the pseudoepidemic was primarily attributed to variability with the test administration and reading, as well as to the specific type of test used.

The testing of [a] predominantly low-risk population leads to false-positive results in individuals and pseudoepidemics of false-positive TST conversions in U.S. Army populations, Dr. Mancuso concluded, recommending three actions to reduce the occurrence of false positive skin tests and these apparent outbreaks: test only truly high-risk personnel; standardize testing procedures; and use the more reliable of the TST tests, Tubersol, in lower-risk populations such as the U.S. Army.

As always, an individualized assessment of each patients risk of tuberculosis should be used to target testing and treatment of latent tuberculosis infection. In the absence of other risk factors, clinicians and public health officials should interpret reported skin test conversions after deployment with caution, he added.

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