We investigated a sudden increase in the rate of positive QuantiFERON-TB Gold In-Tube results from 10% to 31% at a U.S. academic institution. Direct comparison of the TB antigen tubes with tubes from a different lot number identified that a potential problem with the TB antigen vials in a certain tube lot was the likely cause of the elevated positive rate. The underlying defect remains unknown. This finding warrants refinement of quality control programs by the manufacturer and users.
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Slater et al. (2012) studied this question.