WASHINGTON, D.C. - A study showing that only a fraction of patients at a Chicago hospital clinic who had been prescribed a cholesterol -lowering drug were aware of its subsequent recall underscores the need for more effective recall systems, Dr. Sidney Wolfe, director of Public Citizen's Health Research Group, wrote in an editorial accompanying the study. The study, available online Oct. 31, will be published in the December issue of Pharmacoepidemiology and Drug Safety.