# Breast Cancer Screening

- Background
- Diagnosis
- Diagnosis Grouped
- Diagnosis by Test Result
- Test result Grouped
- Test result by diagnosis
- Diagnosis Highlighted
- Summary

## Background

A test for a medical condition is often classified according to sensitivity and specificity.

Sensitivity (also called the true positive rate) measures the percentage of sick people who are correcly identified as having the condition. Specificity (also called the true negative rate) measures the percentage of healthy people who are correcly identified as not having the condition.

Suppose that a mammogram test for breast cancer using is 80% sensitive and 90% specific. That is, the test will produce 80% true positive results for patients with breast cancer and 90% true negative results for patients without breast cancer. Suppose that 1% of people have breast cancer. What is the probability that a randomly selected patient with a positive mammogram has breast cancer?

The likelihood that a patient with a positive mammogram has cancer is approximately 8%.

This chart represents a sample of 2,000 women, aged 40, who participated in routine screening for breast cancer. Each block represents 1 woman.

Scroll down to find out more.

▼