Process Control for Immunohistochemistry Staining Procedures
Posted 11th October 2017 by Jane Williams
An extensively used technique for evaluating the expression of tissue antigens and their behaviour is known as immunohistochemistry (IHC). In this technique, the primary antibody raised against the specific antigen and a secondary antibody against the primary one is used for detecting specific targets of clinical relevance. IHC has the greatest impact on diagnostic pathology compared to any other technique. Although modern methods of flow cytometry and molecular diagnosis have also contributed enormously, IHC still remains the most relevant solution for various pathological diagnostic problems.
What is IHC?
IHC is a simple technique comprising of three phases; tissue preparation, antibody staining, and analysis of results. A small error in any of these steps may lead to false or inconsistent results. The pre-analytical and analytical variables have a significant effect on the staining outcomes. Most common effects that have a detrimental effect on the staining results include varying concentration of the dyes or antibodies and antibody incubation time and temperature.
Quality control material
The only way of avoiding poor diagnosis is the use of consistent standard tissue as a quality control material. These tissues can enable a pathologist to know about the treatment that the sample has received and they also validate a test. In the traditional methods, a single control is used for a batch of slides. Tissue blocks that are used for obtaining a tissue slice as a quality control material are sectioned repeatedly and therefore, are responsible for the unreliable and inconsistent quality control of the process. In this context, World Health Organisation (WHO) has recommended an in-house quality control to be performed for validation of the testing steps of every single staining test. The control material is tested at the same time and in the same way as the patients’ sample. This recommendation, however, remains unpracticed because of the work and expense involved, and it leads to the failed or false interpretations in clinical diagnosis.
An audit study has shown up to nine percent false positive or negative results of IHC staining tests due to the lack of a control. Moreover, it has been found that a lack of control over antigen density leads to the retrieval of subjective results of pass/fail only. These drawbacks have a serious consequence on the patients’ health. Due to the substandard IHC staining, disease prognosis and treatment of the patient are affected when they either receive an unrequired treatment or are denied of a needed therapy. This calls for an immediate requirement of a process that provides quality control for each pathological staining procedure. In this context, only on-slide controls can provide information about what actually happens to the tissue sample during the analytical phase of staining. On-slide controls present a reliable tool for the detection of suboptimal or unsuccessful slides and can be helpful in avoiding the false positive/negative IHC reports.
The on-slide controls may not be able to exactly interpret the root cause of the failure of the test but are of high importance for preventing any harm to the patients from unintended errors. A product incorporated with such a quality control system can ensure a correct diagnosis, proper treatment, and safety of the patients. Recent FDA approval of the Process Record Slide (PRS) as the only diagnostic slide that provides an on-slide quality control system for evaluating the whole processing experience is a breakthrough step towards an advanced technology for obtaining objective results and improved interpretation of the IHC tests. PRS also contains a gradient that delivers information about the antigen concentration and is all about getting the controls under control.
It is strongly believed that such products, when combined with the advanced technology of whole slide imaging, can bring a revolution in pathological diagnosis and research.
Find out more about our 4th Digital Pathology Congress: Europe. Download the agenda here.
Process Record Slide Limited is a subsidiary of Sino Limited based in Hong Kong. They are platinum sponsors of the 4th Digital Pathology Congress in London.
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