Ankle-brachial index (TBQ), cruro-brachial quotient (CBQ), ankle-brachial index, or occlusion pressure measurement is an examination method that can describe the risk of cardiovascular disease. The test is considered highly specific and sensitive for detecting peripheral arterial disease (PAVD). The risk of dying from cardiovascular disease within one year is reported to be increased up to threefold for patients with pathological values in the ABI. The ankle-brachial index also predicts the risk of apoplexy (stroke) better than the degree of calcification of the coronaries (coronary arteries) and the intima-media thickness of the carotids (carotid arteries).
Indications (areas of application)
- Cardiovascular risk assessment.
- Suspicion of peripheral arterial disease (pAVD).
Before the examination
- No special preparation is necessary for the patient.
- The following points are important for the meaningful determination:
- The patient should have rested lying down for at least ten minutes before measurement
- The measurement is performed twice, each time on the right and left side
- For the interpretation of the values, the lowest quotient is taken as the basis for the diagnosis The procedure
With the patient lying down, systolic blood pressure (first blood pressure value, in mmHg) is measured at the ankle (posterior tibial artery and anterior tibial artery) and upper arm (brachial artery). A quotient is then formed from these values (systolic ankle artery pressure/systolic arm artery pressure). In healthy individuals, the quotient is ≥ 1, because when lying down, the blood pressure at the ankle corresponds to that at the upper arm or it is slightly higher. In vascularly ill individuals, blood pressure at the ankle is lowered when lying down. A pathological ankle-brachial index is an independent risk indicator for increased cardiovascular morbidity and mortality (mortality). If the quotient is lowered below 0.9, this indicates peripheral arterial occlusive disease (pAVD), which in turn is associated with a significantly increased risk of myocardial infarction (heart attack) or apoplexy (stroke). Peripheral arterial occlusive disease is usually just a sign of atherosclerosis (arteriosclerosis, hardening of the arteries), which occurs throughout the body. With the help of the ankle-brachial index, the following stages of pAVD can be distinguished:
| Measured value | Severity of pAVD | Fontaine stage |
| > 1,3 | False high value (suspected mediasclerosis/Mönckeberg’s mediasclerosis)/calcification of the middle wall layer of an extremity artery) | – |
| > 0,9 | Normal finding | |
| 0,75-0,9 | Mild pAVK | I-II |
| 0,5-0,75 | Moderate-severe pAVK | II-III |
| < 0,5 | Severe pAVD – trophic lesions such as necrosis (death of tissue), ulceration (ulceration), gangrene/special form of coagulation necrosis; it occurs after prolonged relative or absolute ischemia (reduced blood flow) and is caused by necrosis | III-IV |
As the severity of peripheral arterial disease increases, the life expectancy of affected individuals decreases dramatically. It may be less than that of some cancers. If metabolic syndrome is present at the same time, the cardiovascular risk doubles again. Wrong or inconclusive values may be present especially in very old persons or in diabetics, as they may present vascular changes that make correct measurement impossible. In any case, patients in whom pathological values in the ankle-brachial index have been measured should be referred for further angiological diagnostics (examination by a specialist in diseases of the vessels), since a pathological ABI is an independent indicator of cardiovascular morbidity (disease incidence) and mortality (mortality rate).