We thank Janssen and Chantelau (1) for their interest in our study (2), which analyzed the efficacy of several commonly used lower-limb arterial screening modalities in diabetes. We demonstrated that qualitative, operator interpretation of the continuous Doppler waveform at the ankle for limbs without critical ischemia was more sensitive than quantitative analysis in detecting peripheral arterial occlusive disease. In our hands, qualitative waveform analysis achieved a sensitivity of 94% and specificity of 66% in the presence of clinically detectable peripheral neuropathy. Pulsatility index and other quantitative waveform analyses invariably failed to detect more severe peripheral arterial occlusive disease, with an overall sensitivity of 52%. In your study of limbs with and without critical ischemia, pulsatility index was demonstrated to achieve greater sensitivity at 87% (3).
There appear to be two fundamental differences between the respective studies. First, this study focused on the ability of commonly used screening methods to detect hemodynamically significant arterial disease not their ability to predict the presence of critical ischemia. Patients with critical ischemia were therefore excluded from our study. Further, we employed a relatively simple, single-crystal, continuous waveform analyzer and not a more complex device with a linear crystal array and color-flow facility. Color duplex imaging with waveform analysis of the lower limb has been demonstrated to be effective in detecting peripheral arterial occlusive disease (4). Our study used this modality as a gold standard not as a screening modality.
It is not surprising, therefore, that the results of quantitative analysis differ between the two studies.
