diseases causing premature morbidity and mortality. The U.S. Preventive Services Task Force has, for example, examined and made recommendations about screening for 53 conditions, including heart disease, several kinds of cancer, infectious diseases, prenatal disorders, and sensory problems. As these and other recommendations and analyses make clear, clinical epidemiologic research confirms the value of some screening tests but does not support claims for others (USPSTF 1996; Russell 1994; Eddy 1991).

Efforts to evaluate screening strategies and to develop evidence-based recommendations for screening can generate considerable controversy. Science-based conclusions (especially when the conclusion is that the evidence for screening is negative, inconclusive, or lacking) can conflict with the understandable public desire to believe that a particular screening test will save lives. A case in point is the controversy over a recommendation from an NCI consensus panel that screening for breast cancer in women ages 40 to 49 should be a matter for women to decide with their clinicians rather than a routinely advised practice (Begley 1997; Eddy 1997; Ransohoff and Harris 1997). Following protests and criticism from some advocacy groups and some members of Congress, a different NCI panel (the National Cancer Advisory Board) recommended routine breast cancer screening for this age group (Taubes 1997) even though many scientists think that evidence is still inadequate to support general screening in this age group.

The discussion in this chapter builds on sections in other chapters of this report that have examined who is potentially at risk of thyroid cancer from I-131 exposure, how great the risk is, and how communication with the public should be structured. It also draws on the literature review and analyses presented in the background paper commissioned for this study (Appendix F). The discussion here also builds generally on the principles of evidence-based clinical practice and public health policy. It recapitulates some of the information on thyroid cancer presented earlier, so that this chapter can be read independently. This chapter reviews.

  • The concepts and principles for screening recommendations.

  • The burden of illness associated with thyroid cancer.

  • The benefits and harms of screening.

  • The tests used for screening.

  • The evidence about test accuracy and the benefits of early detection.

  • The screening recommendations of other groups.

  • This study's conclusions and recommendations.

PRINCIPLES FOR SCREENING RECOMMENDATIONS

The specific conclusions about thyroid cancer screening for exposed persons were developed by the Institute of Medicine (IOM) committee that was described in Chapter 1. In developing its recommendations, the committee examined the



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