Using data from a national sample of Medicare beneficiaries, we showed that travel distance is strongly associated with receipt of DXA in 2005–2006. This relationship persisted even after accounting for differences in age, sex, comorbidity, health services utilization, and a number of other important potentially confounding factors. Over an 8-year period through 2006, there was a two-fold increase in the number of central DXAs performed, and non-facility DXA providers performed approximately two-thirds of these tests. If due to national reduction in DXA reimbursements the non-facility sites were to stop performing DXAs, then based on travel distance, persons living in rural areas would have reduced DXA access. Overall, our data suggest that the availability of DXA is likely to be an important enabling factor [15
] in whether at-risk persons undergo testing or not. This is an important finding since fewer than one-third of older women and only 5% of older men have undergone testing [7
], and thus an unmet need exists based on recommendations from national guidelines [2
]. Moreover, receipt of DXA has been previously shown to be an important mediating factor to promote osteoporosis medication use among high risk persons [8
] that has been linked to a reduced rate of fractures [17
The potential implications of our results are best understood in the context of changes in reimbursement for central DXAs that selectively affected non-facility DXA providers. DXAs performed in 2006 were previously reimbursed by the Medicare program at $139 (including both technical and professional components). After a series of progressive cuts to Medicare reimbursement rates in the non-facility setting, central DXA payments are scheduled to drop to approximately $76 in 2009 and $56 in 2010 [18
]. The net effect of these changes may be to shift a substantial portion of the tests currently being performed in non-facility settings to facility settings or to high-volume non-facility settings. A contraction in the number of DXA providers has the potential to limit patient access to a service that is recommended for a substantial portion of the population.
Travel distance has been previously shown to be an important determinant of the timing of and receipt of important medical services such as cardiac catheterization and radiation treatment for breast cancer [20
]. Unlike the acute or life threatening nature of these conditions, however, DXA is often performed as a screening test and thus the impetus to perform it may be less compelling. Correspondingly, given less perceived need to obtain testing, barriers to access may be even more important [15
], A previous report that evaluated the relationship between travel distance and receipt of DXA in New Jersey found only a weak relationship [21
]. However, as the authors pointed out, New Jersey is a relatively small, urban state and travel distance were likely shorter than would be expected in other states with a higher proportion of rural residents. Indeed, the median travel distance in that report was only 3 miles. In our study, we found that > 99% of urban dwelling persons had travel distances < 10 miles, and the likelihood of receipt of DXA was quite similar for persons who had to travel less than 5 compared with 5–9 miles.
We are cautious in the interpretation of our results of that described the hypothetical scenario of the travel distance after removal of the non-facility sites. Even with declining DXA reimbursement, particularly affecting non-facility DXA providers, it is unlikely that all of them would stop providing this service. A recent analysis that evaluated the relationship between travel distance and receipt of chemotherapy as a result of the Medicare modernization act in 2003 that shifted some oncology services from physician offices to facility settings showed only modest effects of this policy change in terms of travel distance and wait times [22
]. However, a subgroup analysis showed that those most affected were individuals living in rural areas, which is consistent with observations in our study. These results may or may not be generalizable to DXA utilization since chemotherapy services are typically ordered by oncologists, not primary care physicians who account for the majority of DXA ordering [7
]. Moreover, besides travel distance, there likely are a number of factors that would be affected if DXA tests are shifted to facility providers. Possible outcomes/consequences that also may be impediments to access to care include the inconvenience of obtaining testing in a facility that is often not proximate to physicians’ offices, less continuity of care, and higher patient co-payments (e.g. 40% for facility DXAs compared to 20% for non-facility DXAs). Because the life-threatening nature of cancer treatment may provide more impetus to overcome these barriers compared to obtaining screening for osteoporosis, these factors may have a greater impact on receipt of DXA than receipt of chemotherapy.
Our study must be understood in light of some potential limitations. Our distance calculations were based on zip code centroids. Although a majority of our data was based upon 9 digit zip codes, these distances do not necessarily reflect actual driving distance. However, this method has been previously observed to correlate well with driving distance [23
]. Moreover, we showed high agreement between estimated distance and actual distance for those persons who did receive testing (). Our population represented the Medicare Fee for Service population and did not include commercially-insured individuals or those participating in government-sponsored managed care plans (e.g. Medicare Advantage). Travel distance relationships for these individuals may or may not be similar. Finally, we had no measure of DXA capacity or density (e.g. number of DXA scanners per number of persons in a geographic region). Attempting to estimate capacity or density in an administrative claims datasource would likely have limited validity given the large but variable numbers of persons age < 65 and with other types of insurance that ‘compete’ for DXA capacity with the population we studied. For this reason, the hypothetical scenario presented in showing only modest effects on travel distance if non-facility providers are excluded might be overly optimistic. The reasoning is that this analysis assumes an adequate capacity of facility DXA providers to perform tests that would otherwise have been performed by non-facility DXA providers. However, the true impact on travel distance resulting from the reduction in non-facility DXA providers depends upon both the capacity of new or existing facility providers and the acceptability to patients and ordering physicians of obtaining DXAs in these facility settings.
In conclusion, travel distance to DXA provider is an important factor associated with receipt of DXA. Although recent legislative and regulatory changes affecting reimbursement of DXAs performed by non-facility providers may have only a limited impact on travel distance for persons living in urban areas, the effects are likely to be more substantial for rural residents. Additional work to evaluate the impact of these recent and ongoing cuts in DXA reimbursement is needed to determine the extent to which access to this important service has been affected.