EFSA ::. Opinion of the Scientific Panel on biological hazards (BIOHAZ) - Protocol for the evaluation of rapid post mortem tests to detect TSE in small ruminants<sup>1</sup>

European Food Safety Authority (EFSA)

European Food Safety Authority (EFSA)
Opinions

Opinion of the Scientific Panel on biological hazards (BIOHAZ) - Protocol for the evaluation of rapid post mortem tests to detect TSE in small ruminants1

Question number: EFSA-Q-2007-055

Adopted date: 07/06/2007

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Summary


Annex X to Regulation (EC) No 999/2001 lays down rules for the prevention, control and eradication of certain transmissible spongiform encephalopathies and lists the approved rapid tests which may be used within the framework of the EU monitoring programmes. The approval of these tests was based on SSC and EFSA evaluation protocols and its recommendations on the suitability or otherwise of the evaluated tests for inclusion in the EU programme for TSE monitoring.
 
The EC will now launch a new open call for expressions of interest, for rapid tests for use in the framework of TSE monitoring. This call is intended to cover tests for TSE detection ante- and post-mortem in cattle and sheep and goats.  Evaluation of these tests is based on a protocol developed by TSE testing experts and covers different steps including a pre-assessment, an assessment of the application dossier, a laboratory evaluation, approval of the package insert and a field trial.  EFSA was asked by the EC to revise and update the three current protocols for the evaluation of TSE tests in ruminants taking into account the experience gained in past evaluation rounds. 

This opinion reports on the revised protocol for the evaluation of post mortem TSE tests in small ruminants.

In 2003 the European Commission (EC) (DG SANCO and DG JRC and its IRMM) and EFSA, started evaluation of rapid tests for TSE epidemio-surveillance in small ruminants.   During the previous evaluation process, differences were observed between tests in terms of analytical sensitivity. However, the significance of such differences both in term of field diagnostic sensitivity and biological relevance could not be scientifically assessed at the time of evaluation. Moreover, following the implementation of active surveillance programs in the EU using tests that were validated, a new type of TSE (atypical scrapie cases/NOR98) not previously recognized in the EU, was detected in small ruminants. Currently atypical/Nor98 has been detected in a large number of European countries and approximately constitutes 80% of test positive cases identified in EU. Data collected in this EU active surveillance program clearly indicate that all the validated tests do not perform equally toward atypical cases and that difference in performance result in under- or non recognition of various types of scrapie.  

The EFSA Scientific Panel on Biological Hazards (BIOHAZ) has agreed on a revised evaluation protocol which takes into account the experience gained in past evaluation rounds and knowledge accumulated from the active surveillance program. New tests have to successfully pass all stages of the evaluation process. Progress to the next stage requires successful completion of the previous stage and therefore the process can be suspended at any stage of the evaluation.  

This protocol ensures that newly approved tests will not be inferior to previously approved BSE post mortem screening tests.   In addition to previous evaluation criteria, the revised protocol considers each test’s performance with respect to (i) detection of classical scrapie, atypical scrapie and BSE in sheep and (ii) detection of preclinical cases and (iii) limitations posed by analytical sensitivity in comparison with bioassay. The criteria in this revised protocol introduce more comprehensive and higher standards than have previously been approved for validation of small ruminant post mortem TSE tests for classical scrapie and BSE as well as for atypical scrapie.  Considering data available about abnormal PrP distribution in the three recognized small ruminants TSE forms (BSE, classical scrapie and atypical scrapie) the use of brainstem appears to be the best compromise for detection of all TSE agents in small ruminants.  In consequence, officially confirmed (by CRL and NRL) positive/negative brainstem will be used for the evaluation of tests. 

The BIOHAZ panel recommends that tests already approved for the detection of TSE in small ruminants should be required to participate in the new evaluation in order to confirm their robustness and their ability to fulfil the additional performance requirements (e.g. atypical cases and analytical sensitivity). This re-iterates a recommendation of their recent Opinion on the EU TSE Community Reference Laboratory report on batch testing of TSE rapid tests: sample selection and test sensitivity issues[2] . It is further recommended that tests that are not able to meet requirements for detection of all types of TSE (classical scrapie, BSE and atypical scrapie) not be considered for testing small ruminants in the field.  Tests that fail to meet a requirement in respect of a particular tissue type (lymphoid/CNS) should not be recommended for application on that tissue. Finally, taking into account the experience gained in the TSE test batch testing protocol and because knowledge in the TSE field is rapidly evolving, the BIOHAZ panel recommends that a system of periodic re-assessment of test approval based on both test field performance and evolving EU policy objectives should be considered by the Risk Managers.  

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[1] For citation purposes: Scientific Opinion of the Panel on Biological Hazards on a request from the European Commission on a protocol for the evaluation of rapid post mortem tests to detect TSE in small ruminants. The EFSA Journal (2007) 509, 1-31
[2] For citation purposes: Opinion of the Scientific Panel on Biological Hazards on a request from the European Commission on the CRL report on batch testing of TSE rapid tests: sample selection and test sensitivity issues, The EFSA Journal (2007), 443, 1-18.


Publication date: 22/06/2007
Last updated: 22/06/2007