Potency Release Testing of Blood Typing Products
How is potency determined for blood typing products?
Potency testing is a critical component of the release process for intermediate antibody products For Further Manufacturing Use (FFMU) and reagent blood typing products at Merck KGaA, Darmstadt, Germany. This article outlines the standardized methodology used for potency testing, explores the factors that influence endpoint results, defines the acceptance criteria for batch release, and discusses the implications for the Certificate of Analysis (CoA). The goal is to provide transparency and clarity on how potency is evaluated to ensure consistent quality and reliability of blood typing reagents.
Potency testing methodology
Potency testing determines the serological potency of blood typing products through assessment of the Mode End Point (MEP) and Mean Total Score (MTS) of each batch, comparing results against a designated product reference stored frozen at –80 °C.
The potency testing workflow includes the following steps:
- Red Cell Preparation: A 4% red cell suspension is prepared by combining 0.4 mL of washed packed red cells with 9.6 mL of diluent.
- Preparation of Samples: Three individual red cell types are used. Serial doubling dilutions are prepared for both the test product and the product reference to establish comparative endpoints.
- Master Dilution Preparation: Master, serial, two-fold dilutions for potency titrations are prepared. Tubes should be large enough to allow adequate mixing (e.g., 12 x 75 mm test tubes), and a separate clean pipette or tip should be used for each dilution to avoid carryover.
- Potency Testing: A volume of each dilution of FFMU or reagent is transferred to a separate clean test tube. An equal volume of red cell suspension is added to each tube, mixed, incubated (if required), centrifuged, and reactions are graded macroscopically.
- Endpoint Determination: The endpoint for each red cell is the last positive reaction (1+) grade observed. The mode endpoint and mean total score from three potency tests is reported. Agglutination reactions are graded macroscopically using a standardized scoring system to ensure objective and reproducible evaluation.
- Delta T-R Monitoring: For stability monitoring, batches are tested with a liquid nitrogen-stored red cell maintained through the shelf life. Comparisons are made between the batch under test (T), the reference batch (R), and the initial day 0 result to minimize variability.
- Parallel Testing: Batch-to-batch potency and reactivity variation is controlled by testing each batch alongside a product reference stored at –80 °C to maintain consistent testing conditions.
Acceptance criteria, factors influencing results, and the Certificate of Analysis
Potency acceptance criteria require that the Mode End Point and Mean Total Score of the test product match or exceed those of the product reference. This ensures the batch meets predefined potency standards and contributes to minimizing lot-to-lot variability. We do not produce products to meet a specified endpoint or titre; rather, potency is established against a validated reference standard.
Several elements can impact potency test outcomes, including titration diluent, red cell diluent and concentration, red cell phenotype, test tube specifications, incubation conditions, centrifugation, grading method, and analyst technique. Understanding these factors is essential to interpreting potency results correctly.
Each batch of FFMU and reagent blood typing product is accompanied by a Certificate of Analysis (CoA) detailing: Mode Endpoint (MEP), Mean Total Score (MTS), and confirmation of compliance with acceptance criteria. Due to the biological and qualitative nature of the potency assay, reported potency values can vary between batches. To control for assay variations, a product reference is always tested in parallel with production batches.
The CoA reflects batch-specific results with inherent variability in MEP and MTS, driven by the qualitative assay and influencing factors. Acceptance specifications on the CoA are determined through comparative evaluation rather than absolute numerical values. An accurate understanding of this variability benefits both manufacturers and customers by enabling informed interpretation of potency results, ensuring compliance, and fostering transparency.
Our potency release testing for FFMU and reagent blood typing products follows a rigorous, standardized methodology designed to ensure product quality and consistency. To ensure optimal product performance, we encourage customers to conduct their own testing while considering the factors contributing to potency variability highlighted in this paper.
To learn more about our blood typing products and services, visit our Blood Typing page.