Predicted and observed risk of having severe carotid stenosis
| Clinical risk factor | Predicted risk | Observed risk | Number of patients in risk group |
|---|---|---|---|
| None | 6% | 6% | 335 |
| *Bruit only | 43% | 44% | 70 |
| Diabetes mellitus only | 13% | 19% | 32 |
| Previous TIA only | 13% | 15% | 39 |
| Lacunar event only | 3% | 1% | 142 |
| Bruit + diabetes | 64% | 38% | 8 |
| Bruit + previous TIA | 63% | 75% | 16 |
| Bruit + lacunar event | 26% | 39% | 18 |
| Diabetes + previous TIA | 25% | 10% | 10 |
| Diabetes + lacunar event | 7% | 18% | 17 |
| Previous TIA + lacunar event | 6% | 4% | 28 |
| Bruit + diabetes + previous TIA | 80% | 0% | 1 |
| Bruit + diabetes + lacunar event | 45% | 0% | 1 |
| Bruit + previous TIA + lacunar event | 43% | 20% | 5 |
| Diabetes + previous TIA + lacunar event | 13% | 50% | 4 |
| All four factors | 64% | - | 0 |
TIA=transient ischaemic attack.The predicted risk for the group with no clinical risk factors was assumed to be equivalent to the observed risk. Using this risk, the predicted risks for all the other groups were calculated using the ORs in table 2. The observed risk is the percentage of patients with clinical risk factors who have severe carotid stenosis in our data set. * Bruit refers to ipsilateral bruit.