Diagnostic immunohistochemistry use in Belgian laboratories

In Belgium, the use of IHC testing has grown in the last decade. However, there is a lack of information on the specific indications for which it is reimbursed. The aim of the study is to offer an overview on the use of diagnostic inmunohistochemistry (IHC) testing and its recent trends. Our analysis is limited to reimbursed use, which in Belgium is restricted to a maximum of 4 different IHC stains per sampling session for diagnostic IHC. Consulted sources included data from the compulsory health insurance, and data extracted from a sample of pathology reports gathered from Belgian laboratories for the year 2019. Over the last 10 years, the use of IHC in Belgium grew from 729 030 stains in 2012 to 1,194,331 in 2019, an increase of 63.8 % while the increase in the number of histological or cytological examinations was 13.3 %. The main stains used in 2019 were H. pylori, Ki-67 and broad spectrum CK, which were used in multiple body sites, reflecting the difficulties to identify specific indications. The gastro-intestinal tract is the body site with the highest number of IHC stains (38.2 % of all stains performed), and the most frequently used stain in gastro intestinal biopsies were H. pylori (43.1 %), and CD3 (6.8 %). This study offers an overview of the most frequent indications for which diagnostic IHC staining is used in Belgium, and reflects the evolving nature of this field, highlighting the importance to increase clarity and improve data collection. •The use of IHC in Belgium increased by 63.8% from 2012 to 2019.•The main stain used in 2019 was Helicobacter Pylori.•The highest number of IHC stains are performed on samples from the gastro-intestinal tract.•This study highlights the importance to increase clarity and improve data collection in the use of IHC staining.