A UK NEQAS ICC and ISH multicentre study using the Kreatech Poseidon HER2 FISH probe: intersite variation can be rigorously controlled using FISH.

Aim: To assess a new HER2 fluorescence in situ hybridization (FISH) test and report on multicentre intrasite and intersite variation.

Methods And Results: HER2 results were scored from 45 breast cancers in eight laboratories using the Kreatech Poseidon HER2 FISH probe (Kreatech Diagnostics, Amsterdam, the Netherlands). Overall, 80.