The rapid spread of chronic wasting disease in white-tailed deer highlights the need for new detection tests that can quickly and rapidly detect the presence of disease.
Real-time quaking-induced conversion (RT-QuIC) is a promising research tool for rapid detection of the prions causing CWD. However, success in research isn’t the only thing needed for a new method to become a widely-used diagnostic. Before new detection tools can receive the federal stamp of approval, they must undergo a rigorous series of validation tests to prove that they are comparable to (or better than!) than existing “gold standard” detection tools. One of the first hurdles that a new detection tool has to clear before it can be considered for widespread use is inter-laboratory comparison; we need to know if the test can provide consistent results when used by different people with different pieces of equipment in different locations.
We conducted a multi-institution laboratory comparison to assess whether RT-QuIC is accurate and consistent at detecting CWD in white-tailed deer retropharyngeal lymph nodes (RPLN, the same sample type currently used in other CWD tests). This first comparison used “in-house” RT-QuIC protocols at each laboratory to test a shared set of 50 samples from both CWD-detected and CWD-non detected animals with variable prion protein genotypes. All participating laboratories successfully identified the true disease status despite different deer genotypes and produced results that were consistent across laboratories. The results suggest that RT-QuIC is a promising new detection test for finding CWD prions in commonly collected diagnostic samples.
Despite our findings of result accuracy and consistency across several labs, we did not test every protocol currently used, and therefore cannot conclude that RT-QuIC is robust to every laboratory decision. Rather, our study showed that RT-QuIC is promising, but its uptake should be further strengthened by the installment of a national standardized protocol. After all, standardized protocols and analytical pipelines are crucial to ensure result consistency.
Different lab protocols successfully determined CWD status in RPLN tissues with various genotypes at codon 96, a site in the prion protein that affects a deer’s CWD infection progression. This demonstrates a second promising result that RT-QuIC may be largely robust to genotype at this site. However, one sample with a variable genotype at a different prion protein site (codon 95) failed to show consistent CWD characterization across labs, stressing the importance of deer genetics in future CWD detection test evaluations. Thus, we recommend rigorous genotyping whenever RT-QuIC is assessed for accuracy in the future.
Our results suggest that RT-QuIC is comparable in diagnostic sensitivity to currently approved tests ELISA or IHC, with the added benefit that it has the potential to be faster and more sensitive. This efficacy is promising for future benefits like expanding CWD testing tools and potentially streamlining approval processes for new detection methods.
Read the scientific publication: Darish JR, Kaganer AW, Hanley BJ, et al. Inter-laboratory comparison of real-time quaking-induced conversion (RT-QuIC) for the detection of chronic wasting disease prions in white-tailed deer retropharyngeal lymph nodes. Journal of Veterinary Diagnostic Investigation. 2024;0(0). doi: 10.1177/10406387241285165
