TBI or not TBI: that is the question. Is it better to measure toe pressurethan ankle pressure in diabetic patients?

Aims Measurement of ankle blood pressure is a simple method of assessing lo wer limb arterial blood supply. However, its use in diabetes has been quest ioned due to the presence of medial artery calcification. Measurement of to e blood pressure has been advocated as an alternative but it is technically more difficult. The aim of this study was to obtain information to guide c linicians as to when pressure measurements should be taken at the toe. Methods Ankle brachial index (ABI) and toe brachial index (TBI) were measur ed by Doppler ultrasound, or photoplethysmography on 174 subjects with diab etes and 53 control subjects. The Bland and Altman method, and the Cohen's method of measuring agreement between two tests were used to compare ABI wi th TBI. Results The mean differences between ABI and TBI in control and diabetic su bjects are +/-0.400.13 and 0.37 +/-0.15, respectively. Nearly all diabetic patients with an ABI <1.3 have an ABI-TBI gradient falling within the norma l range established from the non-diabetic cohort. In contrast, the majority of diabetic subjects with an ABI <greater than or equal to>1.3 have ABI-TB I differences outside this range. When patients are categorized according t o ABI and TBI, there is also good agreement between the tests when ABI is l ow or normal (84% and 78% agreement, respectively), but not when ABI is ele vated. Conclusion In the majority of patients with diabetes, assessment of TBI con veys no advantage over ABI in determining perfusion pressure of the lower l imbs. Only in those patients with overt calcification, which gives an ABI g reater than or equal to1.3, are toe pressure measurements superior. This gu ideline should simplify assessment and treatment of diabetic patients with disease of the lower limbs.