Background: Doppler-based measurement of the ankle: brachial index (ABI) has long been regarded as the standard by which to objectively quantify the degree of lower extremity arterial occlusive disease, but this method fails to account for the contribution of systemic blood pressure to actual limb perfusion. We hypothesized that the absolute blood pressure would be a better predictor of the severity of symptoms of chronic occlusive disease than the ABI.
Experimental design: retrospective comparative study.
Setting: university inpatient/outpatient vascular laboratory.
Patients: 1396 evaluable patients out of 2436 total consecutive patients referred with suspected lower extremity arterial occlusive disease.
Measures: comparison of absolute ankle and digital pressures and ABI according to severity of symptoms of chronic lower extremity ischemia using three-way analysis of variance (ANOVA), likelihood ratios, and receiver operator characteristic (ROC) curves.
Results: The symptoms of tissue ulcer/gangrene, rest pain, and gangrene were characterized by differences in absolute pressures in the great toe (47 +/- 42 mmHg vs 55 +/- 40 mmHg vs 62 +/- 33 mmHg [mean +/- SD], F = 19.05, p < 0.001) and ankle (92 +/- 53 mmHg vs 98 +/- 44 mmHg vs 106 +/- 37 mmHg, F = 12.91, p < 0.001), but not by the ABI (0.71 +/- 0.33 vs 0.68 +/- 0.34 vs 0.71 +/- 0.28, F = 1.24, p > 0.05). ROC curves confirmed absolute digital pressure (area under curve [AUC] = 0.628) and absolute ankle pressure (AUC = 0.607) to be superior to ABI (AUC = 0.572).
Conclusions: The severity of symptoms for peripheral vascular disease correlate better with absolute pressure measurement than with ABI.