Age-specific and age-adjusted penetrance as Poison Center outcome measures

Background: The American Association of Poison Control Centers defines pene trance as the number of exposures per 1000 residents of a population during one year. This metric fails to account for confounding ky age group variab ility. We demonstrate the error caused by using raw penetrance and present two alternate methods of calculation, age-specific penetrance and age-adjus ted penetrance. Methods: Data from the toxic exposure surveillance system w ere collected from calls to our 41 county regional poison centers in 1998. Age-specific penetrance (ASP) was calculated by dividing the number of expo sures (E) in age interval "i" in county "A" by 1000 population in age inter val "P," in county "A" or ASP = E-i/Pi. AAP is the summation of the weighte d age-specific penetrance. Weights (w(si)) represent the relative age distr ibution of a standard population, in this case the 1998 US population. AAP = Sigma (i) w(si) (*) E-i/P-i. [GRAPHICS] County C has low raw penetrance and is known to have relatively fewer toddl ers and presumably a lower incidence of poisoning. This demonstrates that r aw penetrance misrepresents populations with small proportions of children anti should not be used to compare promotion or prevention activities betwe en populations. Conclusion: We recommend poison centers and the American As sociation of Poison Control Centers replace raw penetrance with age-adjuste d penetrance us one measure of the effectiveness of a poison center's aware ness efforts.