There are a number of diseases for which early detection is important enough to justify screening large segments of the population. For the screening to be worthwhile, an effective medical intervention must be available that can treat the disease of interest at an early stage. (However, not all of the screening tests that are justified in clinical practice are useful as access indicators.)
Two sets of screening tests—clinical breast examinations (physical palpation by a health care professional) and mammography for detecting breast cancer, and Pap smears for detecting cervical dysplasia and the less commonly occurring invasive cervical carcinoma—have high sensitivity and high yield; they also detect conditions with high prevalence. Moreover, morbidity and mortality from these cancers are reduced when they are detected at an early stage and the patient is treated appropriately. The timing of the screening tests depends on the age and risk profile of the woman being tested. In most cases the earlier in its progression that the disease is detected, the greater the chance of preventing cancer-related mortality.
For some women less than optimal use of these screening tests indicates the presence of one or more barriers to primary health care services. Yet for other women the failure to undergo a recommended screening test may reflect a lack of knowledge about the test's benefits or insufficient counseling by the woman's health care provider. These latter circumstances are less clearly a problem of access to health care than an indication of poor quality or inadequate medical care. If specific groups consistently receive substandard care, however, this could indicate the presence of an access barrier.
The measure of utilization of breast cancer and cervical cancer screening tests is the percentage of women in specific age groups who undergo the procedures during a given time period. Two of the primary sources of data for monitoring the use of cancer screening services are the National Health Interview Survey (NHIS), conducted periodically by the National Center for Health Statistics, and the Behavioral Risk Factor Surveillance System, a state-based program of periodic surveys sponsored by the CDC. The most recent data on mammography come from a special survey completed in 1990, the Mammography Attitudes and Usage Study.