IHControls® are intended as on-slide controls to verify correct performance of the stain on each and every slide. Since IHControls are not comprised of tissue or cells, there is no possibility that they could be confused with the actual patient sample.
Reproducibility – IHControls are the same day to day over the course of the year. Patient tumors are, by definition, variable and non-standardized.
Ease of use – The first step in creating a conventional tissue control is to find a suitable case from the paraffin block archive. Typically, a period of time must pass (years) before a patient tumor sample can be considered a “discard,” for use as a staining control. The block must then be microtome-sectioned and the sections mounted on microscope glass slides. In comparison, IHControlsare available off-the-shelf, as is normal in other clinical laboratory disciplines. Applying a 1-microliter droplet of IHControls is accomplished in a relatively easy and straightforward manner.
Antigen retrieval – Formalin-fixed paraffin-embedded tissue controls generally require antigen retrieval, testing an important aspect of the total IHC stain process. The same is true for IHControls, which also generally require antigen retrieval for optimal IHC staining. The utility of IHControls in verifying proper antigen retrieval has been tested and published (1).
Quantitation – Tissue controls are heterogeneous. IHControls, on the other hand, are specifically designed for standardized quantitative measurement, facilitating inter-laboratory comparison of staining intensity. IHControls include internal negative and positive color standard microbeads to compensate for differences in microscopy.
Internal specificity checks – Tissue controls have a built-in set of specificity checks, comprising other antigenically irrelevant proteins. IHControls also have internal specificity checks, comprising at least one other microbead type coupled with an irrelevant antigen.
Role in pre-analytic verification – Leftover paraffin-embedded tissues that were fixed, processed, and embedded at some date in the past do not serve as a control for those processes on future days. The same is true for IHControls. Neither serves as controls for pre-analytic variables.
(1) SR Sompuram, K Vani, AK Schaedle, A Balasubramanian, & SA Bogen. Selecting an optimal positive IHC control for verifying antigen retrieval. J. Histochem. Cytochem. 2019 67(4):275-289.