Summary: Allergy diagnosis is a complex, multi-stage process consisting of a medical interview, a physical examination, and additional tests, among which in vitro tests are crucial. These tests detect and measure allergen-specific IgE (sIgE) levels. The goal of this test is to support the process of identifying, as precisely as possible, the allergen causing the patient's allergic symptoms. Detecting the allergen significantly facilitates diagnosis and the implementation of effective therapeutic solutions, ultimately improving the patient's quality of life. Currently, many different tests are available for determining sIgE in blood. Laboratory tests differ in their significant analytical characteristics, which results from their design, the technological solutions used, and the analytical and measurement systems used. The test model and its components (substrates, reagents, reaction conditions, detection method) are fundamental elements determining the technical and functional characteristics (including sensitivity and specificity) of immunochemical methods (including sIgE determination methods), which translates into the quality, reliability of the obtained results, their clinical utility, and the appropriateness of a given test format for the diagnostic process. These are also significant reasons for the incomparability of sIgE results obtained using different analytical methods. The variety of available analytical systems makes knowledge of the technology used for sIgE determination essential for the proper selection of a laboratory method and subsequent clinical interpretation of the test result obtained using a given method in the context of allergic disease symptoms and the patient's medical history. It is also important to remember that test quality is only one of many factors influencing the quality of laboratory test results, and sIgE determinations intended for use in the diagnostic process must be performed in a medical diagnostic laboratory by individuals with the appropriate qualifications and authorizations to perform them, in compliance with the required quality standards.