This study examined the delivery and receipt of CRC screening among a nationally representative sample of Medicare beneficiaries according to the specialty of their usual PCP. We found that the use of CRC screening tests, defined in our study as having completed FOBT testing within one year or sigmoidoscopy or colonoscopy within 5 years, was lower than the national goal of 70% for both internists and family physicians despite high levels of CRC screening awareness among beneficiaries. We found that patients receiving care from FPs had a lower rate of testing than those receiving care from internists, despite equal or higher awareness of screening tests among FPs' patients. PCP specialty differences were observed for all testing outcomes examined and remained statistically significant even after accounting for socioeconomic status of enrollees and factors related to access to health care. Surprisingly, the magnitude of the differences in use of screening tests was similar across many of the subgroups examined. The stability of the results across multiple outcomes, subgroups and multiple sources of information strengthens our findings.
We found a wide spectrum in terms of testing rates in this population. In 2007, 68% Medicare beneficiaries in higher income groups who received care from internists had undergone testing, which is nearly at the national screening target proposed for 2020. We observed the lowest rate, 34%, among disabled enrollees (50-54 years old) receiving care from FPs, which was 50% lower than the rate for this group of enrollees who had received care from internists. Only about half of eligible patients had received an FOBT kit, with proportionally fewer of FPs' patients receiving one. Less than a fifth of beneficiaries who received care from FPs received a screening colonoscopy recommendation, compared to about a third of those who received care from internists.
To our knowledge, no previous studies have simultaneously examined specialty of usual healthcare provider and patients' receipt of CRC screening in a nationally representative sample. That said, our findings with respect to specialty differences in screening rates are consistent with previous studies showing that among adult PCPs, internists have higher rates of providing preventive care services including cancer screening than FPs [16, 17]. A study using Medicare claims data found that patients receiving care from FPs/GPs were less likely to undergo CRC screening compared to patients of internists . Our study used data from in-person interviews with patients, supplemented with insurance claims, and included analyses on multiple CRC screening outcomes at both the patient and provider levels. This provides a more detailed analysis of patient characteristics, patient knowledge of screening services and use of screening tests based on the primary care specialist seen.
The most plausible reason for PCP specialty differences in screening is that family practitioners are less aggressive about offering CRC testing to their patients. Patients receiving care from FPs were equally knowledgeable about CRC screening and Medicare's benefit for screening, as those receiving care from internists. In fact, compared to internists, a higher percentage of patients receiving care from FPs had heard of colonoscopy, and yet screening-eligible patients of FPs were less likely to have been offered a home FOBT kit or a recommendation for colonoscopy. Our findings suggest that once offered screening, the rates of test completion were similar for both groups of patients. These findings suggest that the lower rates of CRC screening are due, in part, to potentially remediable healthcare provider variations in screening practices and not solely from patient-related factors or systematic refusal of testing by patients. Our results show that eliminating PCP variations in CRC practices has the potential to substantially increase utilization of CRC screening among a diverse group of screening-eligible adults.
There are other possible explanations for the PCP specialty variations found in this study. Some previous studies suggest that FPs may be more likely to provide safety-net care in non-academic and rural settings [17, 18]. This could have a significant impact on recommendation for colonoscopy as FPs may have less access to subspecialist referral networks necessary for colonoscopy. Further, FPs provide a wider scope of services , which may lead to more competing and disparate demands in their practices than for internists . However, in this study, the differences persisted even after controlling for patient factors, suggesting that differences in use of screening tests cannot be attributed to differences in the complexity of patients' medical care needs alone.
Organization and style of physician practices, such as tracking systems for monitoring delivery of CRC screening services, may contribute to the differences observed in this study [17, 18]. Such practice-related barriers to providing CRC screening may present greater hurdles for FPs than internists, particularly in rural and underserved areas. Tailored practice-based interventions  including reminder systems , clinical outreach, programs to monitor disparate care in practices, and the use of preventive medicine specialists, supported by information technology solutions and incentive programs, may increase screening within primary care offices. Mitigating such hurdles has the potential to increase recommendations of CRC screening in primary care practices.
Limitations and strengths
Measures of CRC testing were based on self-report, which can be subject to considerable recall bias. Self-report may overestimate screening rates [27–29], or, on the other hand, may capture information not captured in claims, particularly for those with supplemental insurance, who may not have valid claims in Medicare databases . Also, the use of colonoscopy or sigmoidoscopy was defined as being within a 5-year time period rather than the 10-year period recommended by some guidelines. The screening rates may have been higher if the exposure measurement considered a 10-year period prior to the interview date rather than the interval used for this report. However, screening colonoscopy was relatively uncommon in the early 2000s . Thus, extending the window for ascertainment of colonoscopy is unlikely to have a substantive impact on the findings. Also, we were unable to differentiate screening from diagnostic exams. These limitations may result in misclassification of some of the outcomes studied. The misclassification was likely non-differential and thus would not have changed our findings. This study was based on data on Medicare beneficiaries in the United States and as such, may not be generalized to other populations or settings with different health care systems. However, the findings provide important lessons for evaluating and improving the delivery of cancer screening services in primary care for a broad range of settings.