Table VI.
Accuracy of Resting ankle-brachial index (ABI) and toe-brachial index (TBI) in detecting 50% or greater stenosis according to duplex ultrasound (DUS) imaging (whole series)a
| ≥50 Stenosis | Sensitivity | Specificity | PPV | NPV | Accuracyb | P value for accuracyc |
|---|---|---|---|---|---|---|
| All patients | 68 (64.7–71.9) | 85 (82.3–87.7) | 82 (78.9–84.4) | 73 (71.1–75.6) | 77 (74.6–79.1) | |
| Diabetics | ||||||
| Diabetics | 64 (59.0–89.9) | 78 (72.0–82.7) | 81.5 (77.5–84.9) | 59 (54.9–62.1) | 69 (65.7–73.0) | <.0001 |
| Nondiabetics | 74 (68.6–78.8) | 89 (86.1–92.0) | 82 (77.8–85.9) | 84 (80.9–86.2) | 83 (80.3–85.8) | |
| CKD | ||||||
| CKD | 63 (53.2–71.2) | 86 (77.6–92.1) | 84 (76.4–89.9) | 66 (60.0–70.9) | 73 (66.8–78.9) | .1562 |
| Non-CKD | 70 (65.6–73.4) | 85 (81.9–87.8) | 81 (78.1–84.2) | 75 (72.4–77.3) | 78 (75.1–79.9) |
CKD, Chronic kidney disease; NPV, negative predictive value; PPV, positive predictive value.
Values are presented as percentages (95% confidence interval).
a
Abnormal is defined as follows. If the ABI is abnormal, it is abnormal. If the ABI is normal/inconclusive and the TBI is abnormal then it was coded as abnormal. All others (ABI would be normal/inconclusive) are coded normal/inconclusive.
b
Accuracy = (True positive + True negative)/(True positive + True negative + False positive + False negative).
c
χ2 test.