What to know
- Presentation Day/Time: Friday, April 25, 10:55 am–12:20 pm
What did we do?
- Over the last decade, large reference laboratories have shifted from titered serologic assays for Francisella tularensis to qualitative assays with higher sensitivity but lower specificity. We assessed if changes in serologic testing are associated with changes in case investigation outcomes.
What did we find?
- Data from eight states were included, with 358 investigated cases during 2014–2018 and 361 during 2019–2023.
- Comparing these periods, the proportion of investigated cases with positive titered serology decreased (from 22.9% to 15.5%) while proportion with positive qualitative serology increased (from 22.9% to 59.3%).
- Concurrently, proportion of investigated cases classified as confirmed decreased (from 39.4% to 16.9%), the proportion classified as probable was similar (from 29.3% to 25.2%), and the proportion considered non-cases increased (31.3% to 57.9%).
- Among 214 investigations of people with positive qualitative serology during 2019–2023, 130 (60.7%) were considered non-cases.
Why does it matter?
- The proportion of tularemia investigations yielding confirmed cases is decreasing.
- People with positive qualitative serology are frequently considered non-cases, suggesting that tests might be ordered without compatible clinical syndromes and might reflect false-positive results.
- These findings will guide an updated tularemia case surveillance definition that includes stricter laboratory criteria that prompt case investigation.
***This presentation has updated data that will be shared at the EIS Conference.
Abstract Category: Tularemia