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Abstract

ease. For example, it was previously reported that the reactivity of diabetic patients to local heating is impaired, 2 and it should be kept in mind that TcPO 2 is measured at 43°C and then automatically corrected to 37°C.Second, the standard deviations (SD) of TcPO 2 are similar in the two groups: 11 to 12 mm Hg at the chest and 9 mm Hg at the foot. Then the differences between means found between diabetic and nondiabetic subjects are roughly 0.50 SD at the chest and 0.66 SD at the foot level. For an equal cost of false-positive and false-negative tests, mathematically the optimal cutoff point for the discrimination of the two clinical situations would be half way between the two means (according to the authors' results, 55 mm Hg at the chest and 53 mm Hg at the foot). In a Gaussian distribution, only 20% and 26% of a population are in the interval mean Ϯ 0.25 SD and mean Ϯ 0.33 SD, respectively. 3 Then if TcPO 2 should be used as a tool to assess vascular disease or dysfunction, the sensitivity and specificity of TcPO 2 would both be 60% and 63% at the chest and foot level, respectively. Assuming that the prevalence of diabetes in the population is Ͻ10% in Europe, 4 the positive predictive values of a chest TcPO 2 Ͻ55 mm Hg and a foot TcPO 2 Ͻ53 mm Hg to detect a diabetic vascular disease or dysfunction in the population would be Ͻ12% and 15%, respectively.Third, as underlined by the authors, TcPO 2 is primarily used as a key point for the diagnosis of critical limb ischemia, amputation level determination, and wound healing evaluation. Thus, there are two major issues resulting from this article. The first issue is to define whether the difference in chest TcPO 2 can be found in a population of patients referred for critical limb ischemia. The second issue is that in diabetes, a number of factors, including neuropathy, may induce foot lesions independently from the presence of arterial disease. Thus, contrary to the chest TcPO 2 and due to a higher prevalence of foot lesions unrelated to vascular disease, the foot TcPO 2 in diabetic patients with suspected foot ulcer or critical limb ischemia could on the average be higher than in nondiabetic subjects.Thereby, although the difference between the two groups is significant, we think that the discriminative power of the sole resting value for TcPO 2 is insufficient to be useful in clinical practice as an additional diagnostic tool to assess subclinical peripheral vascular disease of diabetic origin.