Quality Control: Use of Normal Tissue to Monitor Protocol Performance

Quality and consistency in immunohistochemistry (IHC) protocol performance is aided by the use of proper control tissue with well-defined cellular elements/structures that reflect changes in protocol performance. This approach was integrated into the development of the new Dako FLEX Ready-to-Use antibodies. For each antibody, control tissue was chosen on the basis of the following three parameters: easily accessible tissue; stable antigen expression between samples of the same tissue type; and changes in protocol performance reflected by changes in staining intensity in defined cellular elements/structures within the tissue. The defined cellular elements/structures were divided into high-expression (HE) and low-expression (LE) Structures. HE structures were generally stable in various protocol settings and served to monitor maximum staining capacity without background staining, whereas LE Structures reflected minor changes in protocol performance. For the vast majority of antibodies, it was possible to identify easily accessible normal tissue as control tissue. The most commonly used tissues were tonsil, colon/appendix, and liver. Within the normal control tissue, a variety of cellular elements/structures showed variable staining intensity. It was critical to evaluate these Structures ill several tissue samples to select HE and LE structures that were stable among samples. In clinical tissue samples, it was typically not possible to identify a specific structure with stable antigen expression. When evaluating the antibody-specific HE and LE Structures in variable protocol settings. changes in protocol performance were reflected by changes in staining intensity. Easily accessible control tissue with well-defined HE and LE structures reflecting variations in protocol performance is a superior tool for monitoring IHC protocol performance. These controls are recommended as part of Dako's new FLEX Ready-to-Use antibody series and can be implemented by laboratories to support quality and consistency in the daily routine. (The J Histotechnol 32(4):158-162, 2009)