Quality Control and Laboratory Management Key Points for CD20 Antibody Reagent (Immunohistochemistry Method)

Reagent management is the foundation of staining stability.

CD20 antibody reagent (immunohistochemistry method) is one of the commonly used antibodies in routine testing in the pathology department, and its quality directly affects the credibility of staining results. When purchasing, laboratories should select qualified products with medical device registration certificates or filing credentials, and verify the applicable tissue types, fixation methods, dilution ratios, and expiration dates in the instructions. Reagent storage must strictly follow the requirements, generally divided into refrigerated storage at 2–8°C protected from light; some unopened reagents may be transported at room temperature but need to be refrigerated as soon as possible. Before use, check whether the appearance is turbid, whether there is precipitate or discoloration, and stop use if abnormalities are present. Each antibody should be recorded with the opening date, number of uses, and remaining volume to avoid contamination or reduced titer caused by repeated retrieval.

Performance verification and lot-to-lot comparison

For newly introduced lots of CD20 antibody reagent, laboratories should carry out performance verification. Routine verification indicators include positive concordance rate, negative concordance rate, repeatability, and minimum detectable concentration. It is recommended to select tonsil, lymph node, or lymphoma tissue blocks known to be CD20-positive and CD20-negative as verification samples. Positive tissues should include germinal centers and mantle zones to evaluate staining at different intensity levels. In lot-to-lot comparison, the same tissue section should be continuously stained and interpreted separately by two or more technicians, and the concordance rate should be within an acceptable range. If obvious differences in staining intensity or background are found between the new lot and the old lot, the retrieval conditions or antibody dilution should be adjusted, and the reason for the change should be recorded.

Key quality control points during the staining process

Immunohistochemical staining is a multi-step process, and fluctuations in any step may affect the detection of CD20 antigen. For tissue fixation, 10% neutral buffered formalin is recommended, and fixation time is generally controlled at 6–24 hours. For antigen retrieval, heat-induced retrieval should be preferred, and the pH value and temperature of the retrieval solution must be stable. During primary antibody incubation, it is necessary to ensure that the section is completely covered by the antibody to avoid drying out; incubation time and temperature should follow the instructions and remain constant. In the chromogenic step, DAB reaction time must be strictly monitored; too long can easily lead to nonspecific background staining, while too short can make the positive signal weak. Positive control, negative control, and blank control should be set for each staining batch, with PBS replacing the primary antibody in the blank control to exclude nonspecific binding of the secondary antibody.

Result recording and continuous improvement

After staining is completed, parameters such as section number, antibody lot number, retrieval method, chromogenic time, room temperature, and humidity should be recorded in detail to facilitate tracing the source of abnormal results. For interpretation, a semiquantitative scoring system is recommended, grading based on the percentage of positive cells and staining intensity. For sections with marginal or diffuse nonspecific background, issues such as insufficient washing times and incomplete blocking of endogenous peroxidase should be investigated. Laboratories can evaluate the difference between their own testing level and that of peer laboratories by regularly participating in external quality assessment or proficiency testing activities. The continuous improvement mechanism includes regularly reviewing quality control data, updating SOPs, and retraining technical personnel, thereby ensuring the stable output of CD20 antibody reagent (immunohistochemistry method) in clinical diagnosis.