Almost all publications described how the test is done and half provided information about possible adverse effects of tests (Table). Only a minority of publications provided specific information about pretest probability (eg, how breast cancer risk changes with age), test accuracy, or posttest probability (Table). Where breast cancer risk was mentioned it was usually given in the form of a lifetime risk of a woman developing breast cancer. However, 13% of publications provided information about the risk of developing breast cancer in the next 5 to 10 years and one gave age-specific risks. Information about test accuracy was given as “not all cancers are detected” by the test (9%) or “9 out of 10 cancers are detected” by the test (7%). Quantitative estimates of specificity and positive predictive value were provided in 1 publication. Information about the probability of disease given a positive test result was given as “About 1 in 20 women are asked to come back for further tests. 9 out of 10 women who are recalled do not have breast cancer” in a few publications. Information about posttest probability given a normal test result was not given in any publication. Results of ratings on other items are available directly from the corresponding author.
TABLE
Percentage of 54 patient education publications rated as providing information on key items about breast cancer screening
| Information about | Publications providing any information (rating 2-5) | Publications providing substantial information (rating 4 or 5) |
|---|---|---|
| How the test is done (%) | 93 | 57 |
| How breast cancer risk varies by age (%) | 37 | 15 |
| Adverse effects of tests (%) | 48 | 9 |
| Test accuracy, ie, false-positive and false-negative results (%) | 18 | 2 |
| Posttest probability given a normal or abnormal test result (%) | 20 | 0 |
Discussion
We found that the quantitative information women need to make informed choices about whether to undergo a breast cancer screening and to fully understand the test results was lacking in most publications. The most commonly used format for expressing the prior probability of breast cancer was lifetime risk; age-specific information was rarely provided. As the risk of breast cancer varies greatly with age, age-specific prior probabilities, not lifetime risk, are needed for informed decision making. Few publications provided information about test accuracy. Failure to acknowledge that tests may give false-positive and false-negative results may mislead people in interpreting their results. For example, people may think that if the test is negative, disease is absent, whereas in reality a negative test reduces but does not eliminate the possibility of disease. Conversely, many tests give positive (or abnormal) results, which prompt anxiety even though disease is absent. In the absence of information about test accuracy it is likely that misconceptions about test results will persist.
Some limitations of the study should be noted. Although publications commonly used in New South Wales (the most populous state of Australia with approximately one third of the total national population) are unlikely to have been missed in this study, we cannot guarantee that all publications currently in use were obtained. Secondly, we acknowledge that the ratings may have been different if others rated these publications. However, it is unlikely that either of these considerations is substantial enough to affect the general direction of the findings.
In conclusion, we suggest that there is an urgent need to ascertain what information consumers need about screening and diagnostic tests so they can make rational, informed choices. Communicating information about pretest probability, test accuracy, and posttest probability to consumers will require careful development and evaluation work. However, this work is essential so that people can give truly informed consent to being tested. Further, good information is needed for those people who want to participate actively in decisions about whether to undergo a test, and to support more accurate patient understanding of test results.