Mammography (Digital) — Breast Cancer
Test Characteristics
| Metric | Value |
|---|---|
| False-negative rate | 13% (sensitivity 87%) |
| False-positive rate | 9% (specificity 91%) |
| Bayes factor | 10× |
| Base rate | 1% of women undergoing screening mammography |
Interpreting Results
| Scenario | Prior | + Result | − Result |
|---|---|---|---|
| Average screening patient | 1% | 10 × 1% = 10%1%× 1010% | 1/10 × 1% = 0.1%1%÷ 100.1% |
| Family history of breast cancer | 5% | 10 × 5% = 50%5%× 1050% | 1/10 × 5% = 0.5%5%÷ 100.5% |
Even with a positive result, 9 out of 10 average-risk women recalled for workup will be cancer-free. Dense breast tissue lowers sensitivity, weakening the negative-test reassurance.
- + result: risk goes from shellfish allergy (1%) to left-handed (10%)
- − result: risk drops to appendicitis this year (0.1%)
Sources:
- BCSC. Screening mammography benchmarks, 2007–2013.
- Rosenberg et al. Radiology, 2017. PMC 5375631.
- Kerlikowske et al. Arch Intern Med, 1996. PubMed 8667537.