Among a population-based sample of health plan enrollees eligible for CRC screening, most patients who went unscreened over a two-year period received several primary care visits during that time. Although receipt of few primary care visits was associated with lack of screening, the fraction of lack of screening that could potentially be attributed to limited primary care exposure (i.e., 0 to 3 visits over a two-year period) exceeded 10% only among men. Among women, the fraction of lack of screening associated with limited primary was substantially less, because a large majority of unscreened women had more than three primary care visits. In similar settings, policymakers and health system leaders may wish to prioritize interventions to optimize opportunistic delivery of CRC screening during existing primary care visits, rather than outreach efforts to encourage primary care attendance among population subgroups that are accessing little or no primary care. Alternatively, programs to promote CRC screening independently of primary care may hold promise.
Research suggests several potential targets for improving the delivery of CRC screening during primary care visits. Because patients consistently cite the importance of a physician's recommendation in motivating CRC screening (4
), health systems should prioritize interventions with proven efficacy in increasing physicians' CRC screening recommendations, including: i) educational programs to increase provider awareness of CRC screening guidelines (18
); ii) systems to prompt patients to inquire about CRC screening (19
) or to remind providers at the point-of-care regarding patient eligibility (20
); iii) financial incentives for providers or patients (24
); and iv) promotion of visits dedicated to the delivery of evidence-based preventive services (8
). Primary care systems could also augment CRC screening by assigning non-physician team members (e.g., nurses or medical assistants) tasks of assessing and counseling patients regarding CRC screening eligibility (27
). Finally, there is likely room for improving the effectiveness of provider counseling regarding CRC screening, as many CRC screening discussions apparently do not conclude with patient uptake of CRC screening (30
Although the strength of the association between limited primary care and absence of CRC screening was similar among women and men, the PAR% was greater among men than women, because a greater proportion of unscreened men had few primary care visits. In addition, the PAR% of limited primary care was highest among younger men (aged 50-59 years). While many women aged 50-59 years may be accustomed to seeking regular primary care services for breast and cervical cancer screening, many men of the same age may be unaware of guidelines recommending CRC screening for adults aged 50 years and older. In addition, younger men may perceive the attendance of a preventive physician visit as contrary to current social norms, suggesting the need for public health messages encouraging men over age 50 years to discuss CRC screening and other evidence-based preventive services with primary care physicians.
Relative risk estimates in our study may be subject to residual confounding by unmeasured patient characteristics that are associated with both primary care attendance and completion of CRC screening. To the extent that unmeasured patient factors explain observed associations rather than visit attendance, our study may exaggerate the true PAR% associated with low numbers of primary care visits. In addition, CRC tests may have been performed for diagnostic rather than screening purposes. Because patients with more primary care visits may be more likely to have tests performed for diagnostic purposes, we may have overestimated the true percent of patients who received CRC screening to a relatively greater extent in strata of patients with greater numbers of primary care visits. Such differential misclassification would tend to inflate PAR% estimates by increasing both the RR associated with low visits and P (the proportion of all unscreened patients that had low visits). In spite of potential biases that may inflate PAR% estimates, PAR% estimates were generally small, so the policy implications of our findings do not seem altered.
The comprehensiveness of the health plan data (including data on patients who received zero primary care visits) enabled us to quantify the impact of primary care use on the delivery of CRC screening to an entire population. Nevertheless, the population was insured by a single integrated health plan with a relatively high degree of primary care access. In other populations with lesser access to primary care, limited primary care use may contribute to a greater extent to slow population uptake of CRC screening.
Among health plan enrollees, limited primary care attendance was associated with a lack of CRC screening, yet most unscreened women and men attended regular primary care over a two-year period. Our study therefore suggests that health plan efforts to increase population use of CRC screening might best prioritize the successful delivery of CRC screening during primary care visits that patients already attend.