The impact of multiplex panel testing on ascertainment of pertussis-attributable, non-infant deaths: national surveillance from England

Understanding the burden of pertussis and pertussis-related mortality is important in enabling a better understanding of population vulnerability and supporting vaccination program planning. However, changes in laboratory practice can have important implications for public health surveillance. This study considers the impact of increasing use of multiplex panel testing for respiratory pathogens on the ascertainment of pertussis-related non-infant deaths, drawing on multiple surveillance data sources from England. Information was sourced from the Office of National Statistics cause of death records, public health case management records, laboratory results collated nationally, and death notifications received via General Practices. Figures covered the period 2023/24, coinciding with a large, national outbreak in England, and were compared with data from 2012—the last major outbreak in England. Of 34 deaths identified as potentially pertussis-related among individuals aged >12 months in 2023/24, 11 ultimately met the pre-defined criteria to be classified as pertussis-attributable; none of the five possible cases identified in 2012 did so. A total of 29 of the 34 (85%) tested positive for pertussis via multiplex panel testing, of which 17 out of the 29 (59%) were ultimately excluded as pertussis-related deaths. Findings highlight significant complexity in the attribution of pertussis-related mortality in an era of widespread multiplex panel testing. IMPORTANCE Correctly identifying deaths caused by pertussis (whooping cough) is important for timely public health action but is not straightforward. We aimed to find out how many deaths potentially caused by pertussis that are notified to national authorities in England are really caused by the infection, in a context where many hospitalized patients are now being tested using multiplex panel testing. Overall, 68% of those cases identified as potential pertussis deaths through regular pertussis surveillance processes in England proved not to have been caused by the infection. This finding highlights challenges to surveillance of pertussis-related deaths in the era of widespread multiplex panel testing use. It may point to the need for clearer guidance concerning the use of this testing approach.