The enhanced peroxidase one step method increases sensitivity for detection of Ki-67 in pituitary tumours

Aim-To compare the Ki-67 labelling index determined using the enhanced pero xidase one step (EPOS) method with that using the standard ABC technique in pituitary tumours. Methods-Adjacent sections were immunostained using the EPOS and ABC techniq ues with the same Ki-67 antibody and same antigen retrieval method. Results-The labelling index measurements with the EPOS Ki-67 antibody were significantly higher than when using the traditional ABC method, and there was a positive correlation between the two techniques when performed on the same cases. This suggests that a higher proportion of cells are within the cell cycle than previously thought, although it gives no direct informatio n on the race of proliferation of the tumour. Conclusions-It appears that the EPOS system is not only more convenient but may be more sensitive than traditional techniques for detecting Ki-67 in t he nuclei of cells, thus demonstrating more accurately which cells have ent ered the cell cycle.