SAN DIEGO – The true incidence of pertussis in recent years in Americans less than 50 years old is estimated to be 58- to 93-fold greater than the laboratory-confirmed reported case count, Philip O. Buck, Ph.D., reported at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
It’s widely accepted that national surveillance systems vastly underestimate the incidence of pertussis because most cases don’t get reported. In order to obtain a more complete picture of the situation, Dr. Buck utilized a regression equation to estimate the proportion of cough illnesses attributable to laboratory-confirmed pertussis.
Bruce Jancin/Frontline Medical news
A closely similar regression model has previously been utilized by other investigators in published studies that provided estimates of the true burdens of influenza (Epidemiol Infect. 2002 Aug;129:99-106) and respiratory syncytial virus (Eur J Pediatr. 2010 Aug;169:997-1008), noted Dr. Buck, director of U.S. Health Outcomes at GlaxoSmithKline in Philadelphia.
He applied the regression model to medical claims for ICD-9-CM–diagnosed pertussis in individuals under age 50 in the IMS PharmMetric Plus claims database for the years 2008-2013. The database includes more than 150 million enrollees. The average reported incidence of pertussis in individuals less than 50 years old during the study years was 9 cases per 100,000 per year; however, the average regression-estimated incidence was 649 per 100,000, a 72-fold greater figure.
During 2011-2013, the 3 most recent years covered by the study, the regression-estimated incidence of pertussis was 93-fold, 62-fold, and 87-fold greater than the reported rates.
Dr. Buck is employed by GlaxoSmithKline, which funded the study and markets pertussis vaccine.