Potential consequences of using Aplisol tuberculin tests in prior epidemic investigations.

To the Editor: Several reports, including one by Shands et al (Infect Control Hosp Epidemiol 1994;15:758-760), indicate an apparent widespread high falsepositive rate associated with the use of Aplisol (Parke-Davis) tuberculin material.lj Numerous other reports indicate that this problem is not recent.2-5 To date, investigators have emphasized the cost and increased frequency of false-positive rates obtained during routine surveillance in healthcam workers (HCW). A second possible consequence of the high false-positive rate observed with Aplisol is an erroneously high rate of conversions observed during outbreak investigations. I did a MEDLINE search of published reports from 1990 through 1994 using two separate word combinations: tuberculosis and healthcare worker, and tuberculosis and hospital. Ten articles reporting on TB outbreaks in the United States that involved tuberculin testing of HCW were identified.“16 None of these 10 articles reported the brand of tuberculin material, or PPD, that was used in their investigations. Two other epidemics that were identified, one involving school children in St. Louis, Missouri, and the other involving an epidemic in a prison in Upstate New York, also failed to report the tuberculin brand that was used in the investigation.17J8 The findings of this survey do not allow one to conclude whether recent outbreaks have used Aplisol, and therefore, whether the reported rate of conversion or tuberculin positivity may be erroneously high. Although it is unlikely that the conclusion of any controlled analyses would be altered, the rates of conversion and infection may be falsely elevated if Aplisol was used. Studies that used Aplisol should be interpreted cautiously, especially if the rate of infection appeared unusually excessive.