Validation of medical tests in laboratories is important prior to implementation of the test in daily routine to guarantee the quality and reliability of the patient results.
But there are two problems: (i) There exist guidelines on validation of immunohistochemical biomarker assays but specific details regarding its application in individual laboratories of anatomic pathology are lacking. (ii) The European IVDR categorizes tests into CE-IVD tests and Laboratory developed tests (LDT) but does not contain a definition on modifications of CE-IVD tests resulting in LDTs and lacks information on how to demonstrate its clinical and analytical performance.
To solve these problems the expert group has elaborated step-by-step instructions for initial analytical verification/validation prior to implementation in daily routine, for revalidation after modification of the test protocol and for ongoing validation, by performing a literature study and a risk analysis. For each type of test, according to its origin (CE-IVD, modified CE-IVD, non CE-IVD) and its intended use (diagnostic, prognostic, pharmaco-predictive), step-by-step instructions on analytical verification or validation have been elaborated by recommending: (i) the number of cases in the validation set, (ii) the performance characteristics (e.g. accuracy, repeatability, reproducibility, sensitivity, specificity) to be evaluated, (iii) the objective acceptance criteria, (iv) the evaluation method for the obtained results and (v) how and when to revalidate.
Our recommendations are intended to help laboratories of anatomic pathology improving, harmonising and standardising their validation procedure. It is a compromise between achievability, affordability and patient safety.
We believe that the application of these recommendations will improve the accuracy of IHC testing, reduce inter laboratory variation and finally increase the overall quality of patient care.