You are a primary care physician advising a 50-year-old woman who is concerned because a friend of hers was recently diagnosed as having breast cancer and has urged her to undergo mammography screening because “it's better to be safe than sorry.”
The woman does not have a family history of breast or ovarian cancer or a breast lump. She asks whether you agree that she should undergo screening. You know that trials of mammography screening support both a mortality reduction from breast cancer and the existence of overdetection and false-positive results, which may result in unnecessary investigations and overtreatment. You are unsure of the magnitude of these effects, which you know are crucial in helping your patient to make her decision. To help, you need to know how screening can be evaluated, how screening test results should be interpreted, and whether there are any valid, relevant, and up-to-date clinical practice guidelines or recommendations about screening for breast cancer.
In this chapter, we probe specific issues introduced in Chapter 26, How to Use a Patient Management Recommendation: Clinical Practice Guidelines and Decision Analyses, focusing on those that are specific to screening (Box 28.3-1).
Issues for Consideration
|Favorite Table|Download (.pdf) BOX 28.3-1
Issues for Consideration
How serious is the risk of bias?
What are the recommendations, and will they help you in caring for patients?
Were the data identified, selected, and combined in an unbiased fashion?
What are the benefits?
What are the harms?
How do benefits and harms compare in different people and with different screening strategies?
What is the effect of individuals' values and preferences?
What is the effect of uncertainty associated with the evidence?
What is the cost-effectiveness?
Clinical practice guidelines by the US Preventive Services Taskforce (USPSTF)1,2 are available online. You obtain the full version of the 2002 USPSTF guidelines, including the systematic review on which the recommendations are based, from their website, as well the 2009 update.
Screening Test Results and Their Association with Underlying Disease
Table 28.3-1 presents the association between screening test results and the underlying disease or risk state. In group A are the people who receive true-positive results and have a patient—important disease. Some of this group will benefit from screening: those who receive effective treatment. For instance, children found on screening to have phenylketonuria will experience large, long-lasting benefits because treating asymptomatic disease is more effective than treating the disease once symptoms develop. Other people in group A will not benefit, despite having a true-positive result: this occurs when finding and treating the disease early do not provide benefit compared with finding and treating ...