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| The pre-validation is made in advance of the formal validation. The histological examinations, serve the verification of functional changes. |
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As an example of the histopathological analysis, we show cross sections of human cornea epithel, which have been handled with an extremelly irritating substance. The histological examination is necessary, at least in some cases, to allow a confimation of MTT test results.
The sketched test protocoll is the result ot of the pre-validations phase. In this phase the following tasks had to be solved:
- Choice of test substance developments of the final test protocol (optimising of the protocol details)
- Evaluation of the comparability of data from different laboratories.
After these activities have been completed, the first phase of the formal validation was started, the testing of 20 coded substances (blind study).
A publication of the results is currently being prepared. The following can already be given away:
- A very sensitive test model has been developped.
- The possibility to reproduce the results in the various laboratories was very good.
- The data show a good correlation with the BCOP.
- With Draize test data an average to good correlation can be shown.
A rather provocative final conclusion was arrived at:
For an in vivo test with high variability it is more difficult, to find an alternative method.
Nevertheless, the new test system is a pleasing development for the following reason: Because reconstructed human tissue is used, it is feasible, that further end points could be measured (i.e. cytokines and growth factors), and with these the test substances could be even better characterised.
The next and final step for the international recognition, the formal validation, will be directly coordinated through the ECVAM, who will then be able to guarantee the independent evaluation of the data achieved. For the formal validation, a relevant number of international laboratories will test a great number of substances in blind tests, whose irritation potential is known as a result of other previous tests.
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