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 peroxidase one step (EPOS) method with that using the standard ABC technique in pituitary tumours. METHODS Adjacent sections were immunostained using the EPOS and ABC techniques 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 information on the rate 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 the nuclei of cells, thus demonstrating more accurately which cells have entered the cell cycle.