Journal of Asthma, 38(2), 127–132 (2001) ORIGINAL ARTICLE Inaccuracy of “Personal Best” Peak Expiratory Flow Rate Reported by Inner-City Patients with Acute Asthma Barry Diner, M.D., 1 Barry Brenner, M.D., Ph.D., 1 and Carlos A. Camargo, Jr., M.D., Dr.P.H. 2 1 Department of Emergency Medicine, The Brooklyn Hospital Center, Weill College of Medicine, Cornell University, Brooklyn, New York 2 Department of Emergency Medicine, Massachusetts General Hospital, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts ABSTRACT Percent predicted peak expiratory ﬂow (PEF) is used to determine the severity of asthma exacerbation and the appropriateness of discharge from the emergency de- partment (ED). The 1995 Global Initiative for Asthma and 1997 National Asthma Ed- ucation and Prevention Program guidelines recommend using a patient’s “personal best” PEF, if available, as a better measurement than the predicted PEF obtained from population-based nomograms. We evaluated the accuracy of personal best PEF as provided by inner-city ED patients with acute asthma. One hundred four patients with acute asthma agreed to return to the ED for repeat PEF measurements on days 3, 7, 12, 21, and 24 after their initial ED visits for acute asthma. At the ED visit, only 29% (30/104) of patients were able to report a personal best PEF. Over the 24 days of follow-up, 45% (10/22) of these patients had a measured PEF greater than their reported personal best. If a predicted PEF of at least 70% was used as the criterion for ED discharge, as several asthma guidelines recommend, then using patients’ re- ported personal best PEF would have led to inappropriate ED discharge for some patients. KEY WORDS: Peak ﬂow; Nomogram; Asthma, Emergency department; Guide- lines. Address correspondence to: Barry Brenner, M.D., Ph.D., Vice-Chairman and Research Director, Department of Emergency Medicine, The Brooklyn Hospital Center, 121 DeKalb Ave, Brooklyn, NY 11201. Fax: 718-250-6528. E-mail: doctor2315@aol.com 127 Copyright C  2001 by Marcel Dekker, Inc. www.dekker.com