Performance analysis of rapid diagnostic tests on atypical bovine spongiform encephalopathy

The preferred method to determine the prevalence of bovine spongiform encephalopathy (BSE) in a country is to use immunology-based rapid-tests. Though these tests are validated to detect C-type BSE disease-associated prion (PrP(sc)), test-specific properties may influence their ability to detect H- and/or L-type BSE PrP(sc), where both are atypical from C-type PrP(sc). Molecular characterization shows atypical BSE PrP(sc) to have a different sensitivity to proteinase activity and different affinities for certain prion-specific antibodies. It is important to understand how atypical BSE PrP(sc) may affect the performance of rapid-tests, which are typically dependent on the use of specific proteases and antibodies. The current study used experimentally generated C-, H-, and L-type BSE PrP(sc) to evaluate 3 tests used in various national BSE surveillance programs: an immunochromatographic assay, a standard sandwich enzyme-linked immunosorbent assay (stndELISA), and a PrP(sc)-conformation-specific ELISA (confELISA). Although BSE PrP(sc) type had some effects on rapid-test performance, analytical sensitivity for atypical BSE PrP(sc) on all 3 platforms was not significantly compromised. When testing for atypical BSE PrP(sc), the 3 tests were able to meet the same requirements that the European Food Safety Authority set when evaluating the tests for C-type BSE PrP(sc).