Offset, imprecision, and stability are essential elements of the analytical performance of most in vitro diagnostic reagents. Among these attributes, offset and imprecision are well understood by manufacturers and laboratory personnel, and many requirements are widely recognized.
However, there are few similar documents on the evaluation of the stability of diagnostic reagents. A large part of this is because although stability is considered a product's ability to maintain stable components, properties, and performance, it is not a property that can be directly measured.
Therefore, the stability requirements of a product can only be derived from the manufacturer's evaluation of specific product attributes over time. Users can only obtain product stability requirements from the product's instruction manual and perform direct verification in the laboratory only through long-term quality control or similar data. Here is the verview of the diagnostic reagent stability test process.
The following four steps need to be followed to establish product stability requirements: provide a definition of the applicability of a given product's stability; draw up a stability test plan to generate experimental data; carry out the plan; the stability requirements are put forward by analyzing the export of experimental data and files.
It is feasible to establish stability requirements by testing the attributes of all products over time, but it is impossible to achieve in most practice due to the huge workload. A more practical method is to test only the key attributes.
The time interval for all key product metrics to meet their respective acceptance criteria within a given statistical confidence is defined as the product's stability duration.
(1) Stability measurement of diagnostic reagents
The first step in the definition of stability requires manufacturers to choose metrics that best reveal a potentially significant change in the quality, safety, or efficacy of a product during the shelf life.
These metrics may reflect the physical, biological, chemical, or microbiological characteristics of the diagnostic reagent itself or the analytical characteristics of the product in use.
The former includes color, pH value, particle size, precipitate presence, biological load, characteristics and purity, while the latter includes measured drift, detection limit, precision of the method for selecting the concentration of analyte, recovery rate and interference offset. Appropriate selection of these metrics can be suitable for qualitative and quantitative definition of the stability of in vitro diagnostic reagents.
The measured drift is a traditional metric for quantitative evaluation of the stability of in vitro diagnostic reagents.
It directly reflects the change in the measured content of a calibrator or quality control product or the ability of a product to be measured in a quantitative sample under certain conditions (for example: time, temperature). This change can be expressed in absolute deviation or relative deviation.
(2) Acceptance standards
The acceptance criteria of key metrics can be derived from the design input requirements of diagnostic reagents, especially its intended use, established quality targets for methods, historical data of similar products, and typical performance of existing products.
Most product stability studies use multiple test samples to evaluate performance within the analytical measurement range of the rectification method. In these cases, the minimum stability interval of any sample will eventually become the overall stability interval of the product lot.
The shelf life study is used to determine the validity period of in vitro diagnostic reagents in the final packaging under the specified storage conditions. This represents the period from the factory to the last day of use, regardless of whether a product is stored under the required conditions or not.
The types of stability research are generally divided into storage period stability research, service period stability research and transportation simulation research.
On the contrary, the diagnostic reagent service life requirement is the time period during which the product remains active after the product is put into use. Examples of this include: The service life of the quality control product after the lid is opened and the service life of a method before recalibration is required.
