Assessment of the pathological stages of Alzheimer's disease in thin paraffin sections: a comparative study

The staging method proposed by Braak and Braak allows the objective and reliable assessment of Alzheimer-related neurofibrillary pathology. Originally the method was designed for 100-microm thick sections. However, the use of thick sections proved to present difficulties in a routine neuropathology laboratory. In order to adapt the staging method for thin paraffin-embedded sections, we performed an inter- and intrarater study analysing the reliability of the staging method in thin sections. Statistical analysis of the data provided by six independent examiners in two rating sessions reveal kappa values of 0.6-0.8 for both the interrater and the intrarater reliability. The average rate of mistake of the examiners was rarely bigger than a half stage. We conclude that the adapted staging method in thin sections is strongly reliable and we recommend it for staging purposes in institutions where the preparation of thick sections would be difficult.