We have read the article by Krishnan et al. (1) with much interest. The article found that there was a difference between foot microcirculation in subjects with and without diabetes, but there was no difference between patients with diabetes with or without foot ulceration. There are points in the methodology and conclusions regarding the microcirculatory investigations that we would like to raise with the authors and would be grateful for their opinion. In the methodology, their assessment of the presence of macrovascular disease comprised ankle pressures and clinical evaluation. These assessments are unreliable in diabetes (2,3). As macrovascular disease could have profound effects on microvascular perfusion, might a more robust arterial evaluation, such as toe pressures or color duplex imaging, have been more appropriate? The groups were not all matched for age or BMI. It has been previously demonstrated that TcPo2 is influenced by both these variables and may confound comparative analyses (2). Further, microvascular assessments are likely to be vulnerable to the influence of local ulceration, compromising the validity of comparison with nonulcerated limbs. Microvascular tests should be performed, therefore, at locations on the foot or distal leg less likely to be influenced by adjacent ulceration. Was an attempt made to limit the local influence of ulceration in those individuals included in the ulcer group that had current ulceration? Regarding medication, although the effect on cutaneous perfusion may be relatively small, their reduction or omission in the diabetic groups would have reduced their potential to influence results. Finally, although the groups were relatively small, further subdivision of the ulcer group into those with active disease and those with healed ulcers may have been more informative.
The presence or absence of ulceration in this study was demonstrated to be associated with worsening neuropathy but not with differences in microvascular function. However, the methodology may have confounded the accurate comparison of microcirculatory function. In the conclusions, the microvascular dysfunction demonstrated in the diabetic groups was compatible with the findings of other workers. Although the reduction in cutaneous perfusion in the groups with diabetes was relatively small, preexisting microvascular dysfunction, when exacerbated by increased tissue pressures consequent to local inflammation and sepsis, may be critical to the development of local ischemia and subsequent delayed healing in diabetic foot disease.