A collaborative study of the histopathological evaluation of the WHO neurovirulence test for poliovirus vaccines.

A collaborative study evaluated the histopathological examination of the WHO neurovirulence test for poliovirus vaccines. Participants scored two sets of slides and the slides were sent to all participants in turn. The results showed an approximately two-fold range in mean lesion scores between readers. As readers scored consistently high or low, however, the range of differences between the two sets of slides was considerably less. From the limited data available, these differences in scoring would not have resulted in different decisions on the acceptability of the particular vaccines included in this study. The study was of value in assisting in developing mutual confidence in the interpretation of histological lesions in the neurovirulence test.