Cervical cancer

The FDA approved the ThinPrep[R] Pap Test[TM], a liquid-based cervical cancer screening test, in 1996 (Johannes 1998) (Cytyc Corporation 2001). Ever since, the ThinPrep Pap test has been rapidly replacing the conventional Pap smear, even though it is about twice as costly as conventional Pap smears (Johannes 1998; Rubin 2002). According to the manufacturer, the Cytyc Corporation of Boxborough, Massachusetts, the test is now used in lieu of a conventional Pap smear in the United States for approximately two-thirds of cervical cancer screenings, a proportion that keeps increasing (Rubin 2002).

Although liquid tests are more effective at detecting precancerous changes and are associated with fewer numbers of ambiguous diagnoses than conventional Pap smears, most of the improvement in test accuracy is in the detection of low-grade lesions that often regress spontaneously (Brown and Garber 1999). Liquid-based technologies have not been shown to be superior to conventional Pap smears at detecting frank cancer and have not been associated with lower mortality from cervical cancer compared with Pap smears. Screening with conventional Pap smears once every three years between the ages of 20 and 75 increases the average woman's life expectancy by about 96 days (Eddy 1990). According to Brown and Garber (1999), annual screening with the ThinPrep Pap test would prolong the average woman's life approximately an additional six hours over annual screening with conventional Pap smears. In triennial screening programs, use of the ThinPrep Pap test instead of conventional smears would prolong the average woman's life about 19 hours (Brown and Garber 1999).

The lower rate of false positive cervical cancer screening tests is one reason for the rapid diffusion of the liquid-based tests, but other factors may also explain their rapid emergence in medical practice. The Cytyc Corporation, the makers of the ThinPrep[R] Pap Test[TM] test (the most commonly used liquid test), actively marketed it to physicians and the general public. The company also encouraged insurance companies to promote themselves to women by including information about their coverage of ThinPrep in advertising campaigns (Johannes 1998).

Articles concerning how physicians learn about new pharmaceutical agents began to appear in the medical literature in the 1950s (Peay and Peay 1994). In recent years, articles have focused on the influences of marketing to physicians on prescription behavior (Avorn, Chen, and Hartley 1982; Manning and Demon 1980) as well as the effect of marketing prescription drugs to the public (Bell, Kravitz, and Wilkes 1999; Wilkes, Bell, and Kravitz 2000; Avorn and Solomon 2000). However, little attention has been given to marketing of laboratory tests used in office-based practice. There is scant information on how office-based physicians choose new diagnostic tests. This paper examines adoption of liquid-based cervical cancer screening tests among family physicians and gynecologists in Maryland. We hypothesized that the efforts of Cytyc Corporation to market the ThinPrep Pap test would be an important determinant of its early adoption by physicians. Additionally, we examined the effects of physician specialty, patient sociodemographics, practice factors, and financial constraints on laboratory decision making on the adoption of liquid-based cervical cancer screening tests.

METHODS

Study Population

The American Medical Association Master File of Physicians was used to create a sampling frame of Maryland family physicians and gynecologists. The selection criteria resulted in a total of 2,025 physicians (1,079 family physicians and 946 gynecologists). Physicians who did not graduate from medical school between 1950 and 1989 were excluded in an effort to restrict the sample to physicians still in practice who had had experience with conventional Pap smears before liquid-based tests were available. Physicians known to be working in federal facilities were also excluded. We randomly selected 250 physicians from each of the two specialty groups using a random number generator. Assuming a 50 percent response rate, this sample size would detect a difference of at least 20 percent in the adoption rates for these groups with a power of .85 (two-tailed alpha of 0.05).

Between July and October 2000, the name of each physician was searched on the web site of the American Medical Association (American Medical Association 2001) and the Yahoo search engine on the Internet for a current Maryland address and telephone number (Yahoo yellow pages 2001).

The medical offices of the physicians were then contacted by telephone to determine if the physician offered routine gynecologic care with screening for cervical cancer. The office staffs of physicians chosen for the study were asked to verify addresses and provide fax numbers. In order to obtain basic information about all physicians in the study, including those who did not eventually respond to the questionnaire, the office staffs were also asked if the physicians use a liquid-based cervical cancer screening test, either the ThinPrep Pap test or AutoCyte (a less commonly used test), conventional Pap smears, or both.

The majority of physicians who were excluded (56.0 percent of the 2,025 physicians considered for the sample) from the study sample before the telephone screen either did not graduate from medical school in the time frame of interest (as determined by the master file of physicians) or could not be located at a current address in Maryland. A minority of physicians was excluded because they were inactive or retired, or because their primary specialty was neither obstetrics and gynecology nor family medicine. In some cases, this information was obtained from the master file, and in other cases, the information was obtained from the yellow pages or during the telephone screen. Physicians whose office staffs indicated that they did not perform routine pelvic examinations were dropped from the study sample (n = 57 of 2,025 physicians in sample frame). Less than 1.0 percent of physicians or their office staffs refused to participate at the time of the telephone screen, and 5.1 percent of physician offices were closed each of three times that telephone calls were made. The reasons for exclusion of physicians from the study were similar for both gynecologists and family physicians except that family physicians were slightly more likely to be excluded from the study for not providing routine gynecologic care (4.2 percent of family physicians versus 1.3 percent of gynecologists).

The final sample of 500 physicians was composed of 23.2 percent of all considered family physicians and 26.4 percent of all considered gynecologists, representing 99.1 percent and 74.1 percent of all physicians listed as family physicians and obstetrician gynecologists in Maryland respectively.

Questionnaire Development

The survey instrument was a self-administered questionnaire with 14 questions and a total of 51 items. Adoption of laboratory tests was viewed in terms of a supply and demand theoretical framework (Rice 1998). Physician and patient factors were conceptualized as determinants of demand while laboratory availability, practice setting, and insurance mix were conceptualized as determinants of supply. The physician factors that potentially influence demand include such variables as specialty, gender, innovativeness, practice location, and attitudes of physicians and their opinion leaders toward Pap smears and new cervical cancer screening technologies. The patient factors that could create demand for a new laboratory test include the sociodemographic mix of the population and patients' risk factors for disease.