both abstinence and contraceptive use appear to be effective in delaying the onset of sexual intercourse and in encouraging contraceptive use once intercourse has begun (IOM, 1997). Currently available contraceptives differentially affect risk of pregnancy and sexually transmitted infections. There is a contraceptive trade-off dilemma with currently existing methods: the contraceptives with the best record of preventing pregnancy have the worst record for preventing sexually transmitted infections (Cates, 1996). For instance, oral contraceptives are highly effective at preventing pregnancy, but offer no protection against sexually transmitted infections. Furthermore, they appear to increase risk of cervical chlamydial infection (Cottingham and Hunter, 1992). Intrauterine devices, also effective in preventing pregnancy, are associated with pelvic inflammatory disease, especially in the first month after insertion (Farley et al., 1992). The condom is effective at preventing sexually transmitted diseases, but it is less effective than are other contraceptive methods for preventing pregnancy (USDHHS, 2000). For such reasons, use of dual methods of contraception could help prevent unwanted pregnancies and transmission of infections (Cates and Stone, 1992; USDHHS, 2000).

DISEASE SCREENING PRACTICES

Screening asymptomatic persons to detect preclinical disease has become an important part of public health. But preclinical screening makes sense only if treatment initiated earlier in the disease process will reduce morbidity and mortality from the disease: there is no benefit in living with a diagnosis if a person’s life or quality of life is not extended. Although some screening tests can be highly effective in reducing morbidity and mortality, others are of unproven benefit. Poor specificity can produce a large number of false-positives, which in turn can lead to unnecessary and potentially harmful follow-up with diagnostic testing and treatment and needless psychological distress.

The selection of appropriate tests for a given individual depends primarily on that person’s age and sex. In addition, consideration of individual risk factors, such as lifestyle or family history, often is used to determine which tests are appropriate tests and how often testing should be done.

In 1984, the U.S. Public Health Service commissioned the U.S. Preventive Services Task Force. This panel was charged with developing recommendations for clinicians on the appropriate use of preventive inter-



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