Seventeen studies were included in the review. Twelve (number of participants unclear) provided data on concordance between IHC score and FISH result and only data for these 12 studies were reported; six studies provided data for all IHC score categories. Blinded interpretation of results was reported for only two studies. Standardisation of test procedures and reporting of results were generally poor. In four studies FISH was carried out only in cases of indeterminate (IHC 2+) results.
The proportion of FISH positive results in IHC negative cases ranged from 0 to 20% for IHC 0 cases (eight studies) and from 3.13 to 51.27% for IHC 1+ cases (eight studies). For IHC positive cases (3+), the proportion of FISH positives ranged from 50% to 96% (11 studies). For IHC indeterminate cases (2+), the proportion of FISH positives ranged from 8.3% to 92.3% (10 studies).
Using data from the six studies that reported FISH positive rates for all IHC scores, median FISH positive rates were 3.5% for IHC 0, 5.8% for IHC 1+, 17% for IHC 2+ and 83.5% for IHC 3+.