Expert: PPD lot testing is loosely regulated
April 1, 2002 less than 1 minute read
Expert: PPD lot testing is loosely regulated
Equivalence within plus or minus 20%
Testing lots of tuberculin skin test products for efficacy is a process left more or less to the discretion of the manufacturer, says Elsa Villarino, MD, MPH, chief of the therapeutics and diagnostics section of the Research and Evaluation Branch at the Division of Tuberculosis Elimination at the Centers for Disease Control and Prevention in Atlanta.
The process begins when reagents are made up in big batches. Each batch is tested in humans by using it in groups thought to be, respectively, TB-infected and uninfected. Those results are compared to results from the standard reagent, which is called PPD S-1.
Next, Villarino says, the batches are broken down into smaller lots. The lots are tested for efficacy in guinea pigs; results from those tests must match the standard results by a margin of plus or minus 20%. Testing of lots is strictly voluntary, she adds. Thus, although the Food and Drug Administration provides companies with guidelines for lot testing, the federal agency has no standards for the testing and exercises no regulatory control over the process, she notes. "Companies do the testing, but they’re not complying with a regulation; it’s just that they’ve always done it," she notes.
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