Reassessing the normal toe-brachial index in young healthy adults

Objective: The purpose of this study was to measure the toe-brachial index (TBI) in healthy young adults and to compare it with the accepted reference range.

Methods: Medical students from the undergraduate classes at the University of British Columbia were prospectively recruited. Participants were surveyed on physical parameters (height, weight), lifestyle factors (physical activity and type, smoking status, alcohol consumption), and medical history (current medications, medical conditions, family history). Bilateral brachial, ankle (using both dorsalis pedis and posterior tibial arteries), and toe blood pressures were measured by stethoscope, Doppler device, and photoplethysmograph, respectively. Ankle-brachial index (ABI) and TBI were calculated and assessed against published reference ranges. TBI was calculated as the mean great toe blood pressure divided by the average of the higher arm systolic blood pressures.

Results: Seventy-three medical students with a mean age of 24.3 ± 2.0 years without any comorbidity were studied. Participants maintained relatively healthy lifestyles (hours of activity per week, 4.6 ± 2.7; body mass index, 21.9 ± 2.4). Caffeine and alcohol consumption was modest (8.2 ± 8.0 and 1.7 ± 2.6 servings/week, respectively). There were no current or past smokers. No significant differences in lifestyle factors were observed between men and women. Mean brachial blood pressure was 116 ± 10 mm Hg (left) and 120 ± 11 mm Hg (right). Mean TBI was 0.98 ± 0.12 (left) and 0.97 ± 0.12 (right) for men and 0.95 ± 0.21 (left) and 0.94 ± 0.21 (right) for women. The overall ABI was 1.10 ± 0.07 when averaged by gender and side. Whereas men had significantly higher blood pressures in the arm, toe, and ankle compared with women, these differences disappeared when the indices were determined. There were no significant differences in TBI or ABI between men and women.

Conclusions: In comparison to published reference values, the TBI in young, healthy individuals is significantly higher. Whereas no gender difference existed, greater variability of the TBI was observed in women. Further studies are recommended to determine if the threshold for diagnosis of peripheral arterial disease based on TBI should be raised.