While peripheral blood bio-markers help in understanding the systemic manifestations of claudication, it does not reflect what is happening in the muscles and microcirculation. Most of the changes in protein expression are too subtle to be detected in peripheral blood. The ease of acquisition does not correspond to ease of interrogation. The dynamic range of proteins in serum makes analysis very challenging because high abundance proteins tend to mask those of lower abundance; whilst a small number of proteins including albumin, Beta 2-macroglobulin, transferrin, and immunoglobulins may represent over 90% of serum proteins11.