The Persuasive Effects of Message Framing in Organ Donation: The Mediating Role of Psychological Reactance

Analytical solutions for point and variance estimators of the mediated effect, the ratio of the mediated to the direct effect, and the proportion of the total effect that is mediated were studied with statistical simulations. We compared several approximate solutions based on the multivariate delta method and second order Taylor series expansions to the empirical standard deviation of each estimator and theoretical standard error when available. The simulations consisted of 500 replications of three normally distributed variables for eight sample sizes (N = 10, 25, 50, 100, 500, 1000, and 5000) and 64 parameter value combinations. The different solutions for the standard error of the indirect effect were very similar for sample sizes of at least 50, except when the independent variable was dichotomized. A sample size of at least 500 was needed for accurate point and variance estimates of the proportion mediated. The point and variance estimates of the ratio of the mediated to nonmediated effect did not stabilize until the sample size was 2,000 for the all continuous variable case. Implications for the estimation of mediated effects in experimental and nonexperimental studies are discussed.

As the need for transplantable organs increases, waiting lists of patients become longer. We studied the size and composition of the national pool of brain-dead organ donors during a three-year period and, on the basis of these data, considered ways to increase the rate of donation. We reviewed hospital medical records of deaths occurring in the intensive care unit from 1997 through 1999 in the service areas of 36 organ-procurement organizations to identify brain-dead potential organ donors. We examined data on characteristics of the potential donors, the processes of referral to organ-procurement organizations and of requesting donations, and the hospitals. We identified a total of 18,524 brain-dead potential organ donors during the study period. The predicted annual number of brain-dead potential organ donors is between 10,500 and 13,800. The overall consent rate (the number of families agreeing to donate divided by the number of families asked to donate) for 1997 through 1999 was 54 percent, and the overall conversion rate (the number of actual donors divided by the number of potential donors) was 42 percent. Hospitals with 150 or more beds were more likely than smaller hospitals to have potential donors and actual donors (P<0.001); 19 percent of hospitals accounted for 80 percent of all potential donors. Calculations of the number of donors per million persons in the general population did not correlate well with the performance of organ-procurement organizations as measured by the conversion rate. Lack of consent to a request for donation was the primary cause of the gap between the number of potential donors and the number of actual donors. Since potential and actual donors are highly concentrated in larger hospitals, resources invested to improve the process of obtaining consent in larger hospitals should maximize the rate of organ recovery. The performance of organ-procurement organizations can be assessed objectively through the comparison of the number of actual donors with the number of potential donors in the given service area. Copyright 2003 Massachusetts Medical Society