What is the typical inter-arm BP difference, and when is a difference clinically significant?

• A. Small differences are common; a persistent large inter-arm difference (e.g., ≥10–15 mmHg) may indicate vascular disease and warrants evaluation.
• B. A persistent large inter-arm difference is always normal.
• C. Inter-arm differences occur only in stroke patients.
• D. Inter-arm differences are irrelevant for diagnosis.

Answer: (A)

Inter-arm BP differences come from natural variability and measurement factors, so small differences are common and usually not concerning. The important signal is when a difference is large and persists across repeated readings. A sustained inter-arm difference of about 10 to 15 mmHg or more suggests possible vascular disease, such as subclavian or brachial artery stenosis, and warrants further evaluation.

In practice, measure BP in both arms at the initial visit using proper technique (seated with back supported, arm at heart level, correct cuff size), and repeat on separate occasions to confirm persistence. If the large difference is confirmed, pursue further vascular assessment (e.g., duplex ultrasound or other arterial imaging) and assess cardiovascular risk. Statements that large differences are always normal or irrelevant to diagnosis do not fit, because persistent large differences can indicate underlying vascular pathology.