Chapter 34 Health screening
Health screening plays a valuable role in the prevention of illness and the promotion of health. For those who screen positively there is the possibility of early diagnosis or early identification of risk with the resulting benefits of early medical intervention. Those who screen negatively are likely to benefit from reassurance. However, the usefulness of health screening may be limited if the uptake rate is low or if no benefits are obtained by patients found to be positive. In addition, there may be disadvantages to patients if the techniques simply serve to increase their anxiety.
Screening: process and results
Usually those found to be positive will go on to have further tests which will determine whether the first result was a true or false positive. Since no screening test is perfect, there will always be a number of false positives and false negatives and the number will depend on the sensitivity and specificity of the test. The four possible outcomes of screening are shown in Figure 1.
Uptake of screening
Those offered a test may refuse to take it because it is incompatible with their health beliefs (see pp. 72–73); for instance, they may not think they are susceptible to the condition being tested. For example, women were more likely to have amniocentesis if they thought they were likely to have a Down’s baby; and uptake was related to perceived risk, but not to actual risk as indicated by the maternal age. Patients may also decide not to have a test, e.g. declining a faecal occult blood test for colorectal cancer because the test is unpleasant.
