Abstract
BACKGROUND: Millions of women receive clinical breast examination (CBE) each year, as either a breast cancer screening test or a diagnostic test for breast symptoms. While screening CBE had moderately high specificity (approximately 94%) in clinical trials, community clinicians may be comparatively inexperienced and may conduct relatively brief examinations, resulting in even higher specificity but lower sensitivity. OBJECTIVE: To estimate the specificity of screening and diagnostic CBE in clinical practice and identify patient factors associated with specificity. DESIGN: Retrospective cohort study. SUBJECTS: Breast-cancer-free female health plan enrollees in 5 states (WA, OR, CA, MA, and MN) who received CBE (N = 1,484). MEASUREMENTS: Medical charts were abstracted to ascertain breast cancer risk factors, examination purpose (screening vs diagnostic), and results (true-negative vs false-positive). Women were considered "average-risk" if they had neither a family history of breast cancer nor a prior breast biopsy and "increased-risk" otherwise. RESULTS: Among average- and increased-risk women, respectively, the specificity (true-negative proportion) of screening CBE was 99.4% [95% confidence interval (CI): 98.8-99.7%] and 97.1% (95% CI: 95.7-98.0%), and the specificity of diagnostic CBE was 68.7% (95% CI: 59.7-76.5%) and 57.1% (95% CI: 51.1-63.0%). The odds of a true-negative screening CBE (specificity) were significantly lower among women at increased risk of breast cancer (adjusted odds ratio 0.21; 95% CI: 0.10-0.46). CONCLUSIONS: Screening CBE likely has higher specificity among community clinicians compared to examiners in clinical trials of breast cancer screening, even among women at increased breast cancer risk. Highly specific examinations, however, may have relatively low sensitivity for breast cancer. Diagnostic CBE, meanwhile, is relatively nonspecific.