 Evidence no. 4 knowledge gaps. In spite of interesting and promising results on allogeneic cord blood platelet gel, three elements are missing before the latter may be used extensively in patients who may need it: 1 a more complete biochemical characterization; 2 a regional or national program to collect and prepare the necessary doses of cord blood platelet gel; 3 a randomized clinical trial of sufficient statistical power to detect significant advantages both clinical and economical in patients treated with cord blood platelet gel versus controls treated with skin ulcer advanced medications. In this regard, small scale investigations suggest that the effective use of platelet gel may reduce recalcitrant skin ulcer medication costs to one tenth of costs currently reimbursed to hospitals for ineffective advanced medication from about 190.000 euro to about 19.000 euro to treat 11 elderly patients. 