Key Objectives:
The objective of this roundtable is to identify strategies to address the challenges of culture-independent diagnostic tests (CIDTs) on surveillance activities at state health departments in the United States. We will discuss protocols state health departments have implemented for prioritization of case investigations, classification of cases when multiple pathogens have been detected from a single patient specimen, acquisition of specimens for subtyping (e.g., pulsed field gel electrophoresis [PFGE] and whole genome sequencing [WGS]), and detection of outbreaks when CIDT-only positive cases are reported. Representatives from state health departments and CDC will share their experiences with CIDT issues, from surveillance challenges to reflex culture of positive CIDTs. We will assess surveillance challenges due to the introduction of CIDTs and successful strategies to address them, identify gaps in knowledge, and discuss how the Foodborne Diseases Active Surveillance Network (FoodNet) and other public health agencies can help address these gaps.
Brief Summary:
In the past four years, the proportion of clinical laboratories using CIDT methods to detect enteric pathogens has increased. In FoodNet, the annual percentage of enteric bacterial (Campylobacter, Salmonella, Shigella, Vibrio, and Yersinia) infections diagnosed with only a CIDT increased from 7% during 2012–2014 to 16% in 2015, and only 63% of laboratories are continuing to confirm positive CIDTs with reflex culture. To accurately count and monitor incidence of infections, national case definitions were recently modified to incorporate CIDT results into case classification protocols for Campylobacter, Salmonella, Shigella, and Vibrio. However, the increasing use of CIDTs creates many challenges to public health surveillance and disease investigation beyond case classification. Unlike culture-based methods, CIDTs do not produce an isolate, which is necessary for subtyping, including PFGE and WGS, and antimicrobial susceptibility testing. Cluster and outbreak detection rely on these subtyping methods, so state health departments or clinical laboratories are burdened with performing reflex culture to obtain this information. In addition, the majority of CIDTs used are syndrome panels that use nucleic acid to detect multiple pathogens with a single test. Identification of multiple pathogens in a single specimen complicates case classification, cluster detection, and interpretation of exposures, symptoms, and patient outcome. This roundtable will facilitate discussion among state health departments and CDC to better understand the challenges of CIDTs and identify strategies to best address them.