Facilities serving vulnerable women had higher diagnostic mammography false positive rates than facilities serving primarily non-vulnerable women. These differences were not accounted for by differences in availability of on-site breast ultrasound or biopsy, academic medical affiliation, or profit status, even though the availability of on-site diagnostic services were associated with higher false positive rates.
Understanding the reasons driving differences in mammography interpretative performance is important to decrease breast cancer disparities and to curb unnecessary healthcare costs. Prior literature reports the excess costs from false positive screening mammography of $500 per mammogram(19
). While specific estimates are not available for the fiscal impact of false positives in diagnostic mammography, likely false positive diagnostic mammography that lead to unnecessary biopsies are even more costly per abnormal reading, as these lead to excess biopsies, instead of follow-up mammography(17
). As many facilities serving vulnerable women fund their mammography centers through foundation grants aimed at increasing access to screening for uninsured women(21
), false positives particularly can drain these limited resources.
Solutions to decreasing disparities in false positive rates start by identifying potential causes. Practice patterns of radiologists working at facilities that serve vulnerable women could account for our findings. Radiologists with more recent training (i.e. less experienced) and who read proportionately fewer diagnostic mammography tend to have higher false positive rates than other radiologists(18
), and such radiologists may more frequently practice at facilities serving vulnerable populations. Radiologists at these facilities may also recall patients more frequently due to recognition that often cancer prevalence and loss-to-follow-up rates are higher among women at these facilities(20
). Interventions to recruit highly experienced, fellowship-trained radiologists may help improve diagnostic interpretive performance at these facilities(25).
Our finding that facilities with on-site diagnostic services have higher false positive rates is consistent with prior research demonstrating that readily available services may be more readily used(21
). However, this finding may be driven by unmeasured characteristics associated with lack of such services at these facilities.
There are several limitations to this study. Income and rural residence was obtained using ZIP code averages, and insurance data was unavailable. We excluded mammography where breast density was unavailable. This study does not evaluate whether the follow-up rates for recalled mammograms differ by facility type. While our findings are consistent with previous work that suggests use of ultrasound increases false positive rates(22
), the prevalence of ultrasound availability is extremely high in our sample, close to 90%. However, availability of ultrasound on-site may not be equated to use in individual women: the BCSC data is unable to consistently ascertain whether a woman actually received ultrasound in this cohort. Our dataset does not capture radiologist characteristics and prior training experience.
Neither on-site breast ultrasound or biopsy, academic medical center affiliation, nor profit status explain the higher diagnostic mammography false positive rates observed at facilities serving predominately vulnerable women. Interventions to improve the accuracy of diagnostic mammography interpretations should consider whether the higher false positives rates are driven by practice patterns of radiologists at these facilities. Recognizing that the availability of on-site diagnostic services may contribute to higher utilization of medical care overall, future studies should evaluate the appropriateness of referrals for biopsy in this context.