The Pap smear gained acceptance as a screening test for cervical cancer in the United States in the late 1950s (Gardner , Lyon). The test is named for Dr. George Papanicolaou, who developed the method from his original work with guinea pig estrus cycles.

Multiple investigators did cytologic work in this area (Ayre), but authors credit Papanicolaou with the "discovery," dating his work as early as 1923 (Carmichael). Papanicolaou’s findings were not adopted by the medical community for another 15 years, so that the "authoritative publications" followed in the 1940s and 1950s (Kaufman). Cervical cytologic screening increased dramatically about 1960 and is now generally accepted. (See indications.)

The Papanicolaou smear as screening tool
The Pap smear fulfills most, but not all, of the criteria for a good screening test as suggested by Sackett (Sackett). First, the burden of suffering warrants screening. Approximately 16,000 new cases of cervical cancer are diagnosed yearly, and about 4800 deaths are attributed to cervical cancer annually (USPSTF). The screening test is generally acceptable to patients. It is affordable and easily incorporated into current health care delivery, although screening programs continue to have difficulty reaching certain underserved populations. Also, patients with an abnormal Pap smear can choose from several options to prevent or delay disease progression.

The Pap smear may not meet the criterion of causation. There is no direct evidence that screening is the cause of the observed reduction in cervical cancer mortality rates. The downward trend in cancer deaths may have preceded the implementation of Pap smear screening (Gardner, Cramer).

Evolving criteria for cytologic classification of cervical cancer and inconsistent implementation of the screening technique further confuse the issue.

Also, the accuracy of the Pap smear has been difficult to verify. Test specificity is probably greater than 90% for cancer and dysplasia, but reported false-negative rates range from 1% to 80% (USPSTF). Because of the Pap smear’s general acceptance and widespread use, a definitive study of its effect on mortality will probably never be done. (See Interpretation of the Pap Smear.)

Other screening tests
Cervicography has been proposed as an alternative screening test for cervical dysplasia. Because of problems obtaining good specimens and poor test characteristics, the test is not currently recommended. Click here for more information.