Surrogate End Points for the Treatment of Diabetic Neuropathic Foot Ulcers
Abstract
OBJECTIVE—The goal of this study was to determine whether surrogate markers based primarily on changes in the size of a wound can be used to correctly predict which individuals with diabetic neuropathic foot ulcers will heal after 12 or 20 weeks of care.
RESEARCH DESIGN AND METHODS—This is a retrospective cohort study using the Curative Health Services database. As many as 39,918 neuropathic wounds on 20,213 individuals with diabetes were evaluated. Seven surrogates based on changes in wound size were evaluated.
RESULTS—Surrogates measured after 2, 4, or 8 weeks of care and based on percentage change in area, log healing rate, and log area ratio discriminated well with respect to differentiating between those wounds that healed and those that did not heal by the 12th or 20th week of care. For example, after 4 weeks of care, the percentage change in area can be used to correctly discriminate 76% of the time between those that healed and those that did not by the 20th week of care.
CONCLUSIONS—The surrogate markers can be used in clinical trials such that shorter and smaller trials can be conducted with reasonable accuracy in order to determine which potential new therapeutics should be studied in larger, longer trials. In addition, the surrogates may also benefit clinicians when they are trying to decide whether a wound care therapy will ultimately be successful.
Footnotes
Address correspondence and reprint requests to David J. Margolis, MD, PhD, Department of Dermatology, Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, Room 815 Blockley Hall, 423 Guardian Dr., Philadelphia, PA 19104. E-mail: dmargoli{at}cceb.med.upenn.edu.
Received for publication 15 May 2002 and accepted in revised form 11 March 2003.
A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
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