Facility characteristics do not explain higher false-positive rates in diagnostic mammography at facilities serving vulnerable women

BACKGROUND: Facilities serving vulnerable women have higher false-positive rates for diagnostic mammography than facilities serving nonvulnerable women. False positives lead to anxiety, unnecessary biopsies, and higher costs. OBJECTIVE: Examine whether availability of on-site breast ultrasound or biopsy services, academic medical center affiliation, or profit status explains differences in false-positive rates. DESIGN: We examined 78,733 diagnostic mammograms performed to evaluate breast problems at Breast Cancer Surveillance Consortium facilities from 1999 to 2005. We used logistic-normal mixed effects regression to determine if adjusting for facility characteristics accounts for observed differences in false-positive rates. MEASURES: Facilities were characterized as serving vulnerable women based on the proportion of mammograms performed on racial/ethnic minorities, women with lower educational attainment, limited household income, or rural residence. RESULTS: Although the availability of on-site ultrasound and biopsy services was associated with greater odds of a false positive in most models [odds ratios (OR) ranging from 1.24 to 1.88; P<0.05], adjustment for these services did not attenuate the association between vulnerability and false-positive rates. Estimated ORs for the effect of vulnerability indexes on false-positive rates unadjusted for facility services were: lower educational attainment [OR 1.33; 95% confidence intervals (CI), 1.03-1.74]; racial/ethnic minority status (OR 1.33; 95% CI, 0.98-1.80); rural residence (OR 1.56; 95% CI, 1.26-1.92); limited household income (OR 1.38; 95% CI, 1.10-1.73). After adjustment, estimates remained relatively unchanged. CONCLUSIONS: On-site diagnostic service availability may contribute to unnecessary biopsies, but does not explain the higher diagnostic mammography false-positive rates at facilities serving vulnerable women.