Key Application Points and Management Requirements of Targeted Antibodies in In Vitro Diagnostic Reagents

Core Role of Targeted Antibodies in Immunoassays

In the field of in vitro diagnostics, targeted antibodies are often used as capture antibodies or detection antibodies in platforms such as enzyme-linked immunosorbent assay, chemiluminescent immunoassay, lateral flow assay, and flow cytometry. Their mechanism of action is based on the high-affinity binding of antibodies to target antigens, converting biological signals into measurable optical, electrical, or color signals. For diagnostic reagents, the specificity of targeted antibodies determines the accuracy of test results; if antibodies cross-react with structurally similar molecules, false positives may occur. Therefore, in the initial stage of reagent development, surface analysis techniques such as immunoblotting and biolayer interferometry are required to verify the antibody recognition profile and exclude nonspecific binding.

Antibody Pair Screening and Pairing Optimization Strategies

Most sandwich immunoassays require the simultaneous use of a pair of targeted antibodies—a capture antibody and a detection antibody. An ideal antibody pair should bind to different and spatially accessible epitopes on the target antigen to avoid mutual competition. Commonly used screening methods include cross-pairing ELISA and surface plasmon resonance technology, selecting high-affinity and non-interfering pairs by determining the affinity constant (Kd) and binding kinetic parameters (such as kon and koff). In addition, in chemiluminescent reagent development, one antibody is often conjugated to magnetic microparticles as the solid phase, and another antibody is conjugated to horseradish peroxidase or alkaline phosphatase for signal amplification. It should be noted that the conjugation process may affect antibody activity, so it is necessary to control the labeling ratio (for example, the molar ratio of enzyme to antibody is generally between 2-4) and evaluate the retained activity after labeling.

Regulatory Requirements for Antibody Preparation and Quality Control

According to the Measures for the Registration and Filing Administration of In Vitro Diagnostic Reagents, immunoassay diagnostic reagents with targeted antibodies as the main active ingredient must submit information on antibody sources, verification information for production strains (viruses) or cell lines, purification processes, and stability study data. Class II and Class III reagents should also establish internal control standards for key quality attributes of antibody raw materials (such as purity, binding activity, and endotoxin content). For example, the purity of monoclonal antibodies is generally controlled to be no less than 95% by SDS-PAGE or high-performance liquid chromatography; titer can be determined by competitive ELISA or relative affinity measurement. In addition, when there are concerns about human anti-mouse antibody interference with murine antibodies, it is recommended to use humanized or recombinant antibody raw materials to reduce background interference. Manufacturing enterprises should establish complete batch-to-batch consistency verification procedures for antibodies and conduct routine management in accordance with the requirements for raw material procurement and inspection in the Good Manufacturing Practice for Medical Devices.

Clinical Evaluation and Post-Market Surveillance of Targeted Antibody Reagents

Before approval for marketing, diagnostic reagents based on targeted antibodies need to verify their performance under the intended use through clinical trials or clinical evaluation. The key evaluation points include sensitivity, specificity, positive predictive value, negative predictive value, and agreement with reference methods. For companion diagnostic reagents, collaborative verification with therapeutic targeted antibodies is also required to ensure the guiding value of the results for medication decisions. After marketing, enterprises should continuously collect adverse event and product quality feedback and carry out risk control in accordance with the Measures for the Administration of Medical Device Adverse Event Monitoring and Re-evaluation. With the increasing demand for precision diagnostics, multiplex targeted antibody detection systems for rare antigens are gradually emerging, and attention to cross-reactivity and batch-to-batch variability in quality control systems will also further increase.