Breast ultrasounds can be "wrong" by failing to detect breast carcinoma (cancer) when it is present. Based on specific studies evaluating the effectiveness of ultrasound in identifying existing cancers, breast ultrasounds miss carcinoma approximately 42.9% of the time.
Understanding Ultrasound Accuracy
When assessing the accuracy of a diagnostic test like a breast ultrasound, various metrics are used. One key metric is sensitivity, which indicates how well a test can correctly identify individuals who have the disease.
Sensitivity and False Negatives
For breast ultrasounds, sensitivity refers to the percentage of actual breast carcinomas that the ultrasound successfully detects. Data shows that the overall sensitivity of ultrasound in detecting breast carcinoma is approximately 57.1%.
This means:
- 57.1% of the time, if breast carcinoma is present, the ultrasound will correctly identify it.
- Conversely, 42.9% (100% - 57.1%) of the time, if breast carcinoma is present, the ultrasound will fail to detect it. These are known as false negatives.
Therefore, when asking "how often are breast ultrasounds wrong?" in the context of identifying existing breast cancer, the "wrongness" refers to these false negative results, where a present carcinoma is missed.
What This Means in Practice
Consider a scenario where breast carcinoma is confirmed through other methods, such as a biopsy (histological diagnosis). For every seven cases of confirmed breast carcinoma, ultrasound imaging might only detect four of them. The remaining three cases would be missed by the ultrasound.
This can be summarized in the table below:
| Ultrasound Outcome (when Carcinoma is Present) | Description | Rate |
|---|---|---|
| Detected Carcinoma (True Positive) | The ultrasound correctly identifies the breast carcinoma when it is truly present. | 57.1% |
| Missed Carcinoma (False Negative) | The ultrasound fails to detect the breast carcinoma, even though it is present, leading to an incorrect "negative" result. | 42.9% |
It's important to note that ultrasound is often used as a supplementary tool to mammography or for evaluating palpable lumps, and its accuracy can vary based on factors like breast density, lesion size, and the skill of the sonographer. While ultrasound is excellent at distinguishing between solid masses and fluid-filled cysts, its ability to definitively identify cancerous lesions requires careful interpretation and often further diagnostic steps.
