By [the fractional factorial] design, the versions of the vignettes with all patient factors present or all absent were the most frequent versions of the vignettes, and the frequency of the remaining versions were uniformly distributed for each vignette. There was no evidence of a systematic under-representation of any versions as a result of non-response.
Perceptions of Guidelines
The respondents’ perceptions of the guideline recommendations for the 4 cancer screening tests are shown in Table 2. Although the respondents’ perceptions of guidelines agreed with the Canadian Task Force guidelines for PSA and mammography, they diverged for colorectal cancer screening. For example, 83.5% of respondents thought colonoscopy was not recommended for patients over 40. A majority of respondents believed that the guidelines for PSA, mammography, and FOBT were conflicting.
The Influence of the Four Principal Factors
Individually, the 4 principal factors were significant determinants of the physician’s decision to order the screening test when the evidence was unclear or conflicting Table 3. The patient’s anxiety about having cancer, their expectations of having a screening test, the quality of the patient-physician-relationship (in most cases), and a positive family history of the relevant cancer all increased the odds of screening. When all 4 factors were analyzed as a combined group adjusting for the presence of other factors Table 3, the principal factors that remained significant determinants of the physician’s decision to order the screening were as follows: anxiety for PSA and mammography; patient expectations for PSA, mammography, and FOBT; a high quality patient-physician relationship for mammography (reduced the likelihood of ordering); and positive family history for all but mammography.
The Combined Influence of the Principal Factors and Physician Factors Physician variables were added to the initial logistic regression models to derive a final parsimonious model for each screening test. Table 4 shows that for each of the screening maneuvers, there were differences not only in the factors that significantly influenced the decision to screen, but also in the magnitude of influence as manifested by the odds ratios. The direction of the influence was similar across examples: all the factors increased the odds of screening except perception that the test is not recommended or does more harm than good, and a good patient-doctor relationship (in the mammography example). PSA and mammography had a similar pattern: patient anxiety, expectations, family history, the physician’s perception of the level of recommendation of the test, whether it creates more harm than good, and the influence of colleagues all significantly influenced the decision to screen. For FOBT, patient expectations, the level of perceived recommendations and the perception of harm were significant. For colonoscopy, patient anxiety, family history, and the perception of the level of recommendation were significant determinants.
Discussion
The results of this study add to the findings from the focus groups and suggest a conceptual framework or model for understanding the determinants of screening behaviour in unclear and conflicting recommendation situations. Although this model offers a more complex picture of the determinants of cancer screening in these instances, there is a great deal of consistency. Patient anxiety, patient expectations, family history of cancer, physicians’ perceptions of the relevant guideline, and physicians’ perceptions of the benefit or harm in screening were all important determinants of screening decisions. One of the important differences in the 2 studies is the relative strength of the influence of family history in this survey study, in particular for mammography and colonoscopy.
Family physicians are trained to heed patient anxiety, but it has only been described as an indirect determinant of cancer screening.12 Patient expectations has been described in the literature in a number of studies as an important determinant of screening.1,13 In addition, other patient-specific factors have been shown to be associated with physician adoption of guidelines, such as patient concerns about finances, quality of life, and location of care.14 Recent research has found an increase in physicians’ wish for more patient involvement in the development of clinical guidelines, and they have suggested that practice guidelines should reflect patient preferences.15
In the final model, the quality of the patient-physician relationship was related to one cancer screening maneuver: mammography for women aged 40-49. It is interesting that a good relationship halved the odds of screening tests being ordered when accounting for other patient factors. The importance of the influence of the patient-physician relationship on screening has been described in previous studies.12,16 In a good patient-physician relationship, patient and physician are more likely to discuss the pros and cons of a conflicting screening guideline and to find common ground than when the relationship is poor.16