The enzyme-linked immunosorbent assay (ELISA) is one of the most sensitive and reproducible assays available. The reproducibility and reliability of the ELISA assays are dependent on proper laboratory technique and careful attention to detail which can cause large variation in the results. There are many different sources of variability of assay results.
- Running Control Samples
To ensure quality control of ELISA assays, it’s important to run assaying control samples across the analytical range of the assay, such as low, medium and high controls. Such controls are typically made from your source analyte and be in the same matrix as your critical samples. By using your source analyte, it’s easy to spot any variation between ELISA assay runs and kit lots.
- Replicate Analysis
Another approach to quality control for your ELISA analysis is replicate analysis which is the repetition of an experiment in order to test the validity of its results. This will allow you to quantify your precision and yield lower %CV. When performing the analysis of the data results it’s important to look at such criteria as %CV and lower limit of detection (LLOD) which will give you criteria for which data points to eliminate.
- Testing for Precision
Precision is the ability of the assay to consistently reproduce a result when sub-samples are taken from the same specimen. Within-assay and inter-assay, precision are two distinct measures that can be made as part of the quality control procedure. There are software programs available that can help you quickly spot such variation in your data.
- Test Storage Conditions
To ensure total quality control of the assay, it’s import to perform stability studies on the storage conditions for your controls. This will verify that your storage conditions are adequate enough and will not cause variation in your assays.
- Laboratory Technique
There are also other non-assay sources of variation that need to be addressed when performing quality control for your ELISA assay. These include how the samples are taken, transported, aliquoted and proper laboratory technique. Once the ELISA assay has been validated, the continued satisfactory performance should be continually monitored by the set quality control process.
When the sources of the ELISA assay variation are identified, it’s simple to implement corrective procedures. The purpose of such quality assessment is to confirm that your ELISA results generated are consistent over time.