Trends in Pertussis Diagnostic Testing in the United States, 1990-2012.

Reports of pertussis have been increasing in the U.S. since the 1990s and pertussis diagnostics have evolved during that time. Here we describe temporal changes in pertussis diagnostic practices in the U.S. during 1990-2012 and discuss potential implications.
Pertussis cases reported through the National Notifiable Diseases Surveillance System (NNDSS) during 1990- 2012 were included in this analysis. Laboratory results were stratified by test type, case classification, age group, and case-patient state of residence.
291,290 cases were included with 64% (n=186,766) reporting at least one pertussis laboratory result. Culture and DFA were the primary results reported during the early 1990s; however, PCR surpassed all other test types during the late 1990s and 2000s. By 2012 more than 91% of cases with known results were tested using PCR, either alone or in combination with another test type. Before 2005, Massachusetts reported 71% of serology results, but an increasing number of states reported serologic results during 2005-2012. When stratified by age group, overall testing trends persist. As of 2012, culture confirmation is used infrequently across all ages, while use of serology increases with age and is most prevalent among adults aged ≥ 20 years.
PCR has become the primary diagnostic method, and serologic assays now are used in a majority of states. Epidemiologic trends must be considered in the context of changing diagnostic tests, and modifications to surveillance case definitions should be considered to better reflect current testing practices.

Authors:Faulkner AE1, Skoff TH, Tondella ML, Cohn A, Clark TA, Martin SW.
Journal:Pediatr Infect Dis J. 2015