Choosing an ELISA Plate Reader

ELISA plate readers were once limited to measuring absorbance across a 96-well microplate. But the technology has moved on. Now, researchers have access to multimode instruments with features designed to streamline experimental workflows. This editorial looks at some factors to consider when choosing an ELISA plate reader for your lab.

Single-analyte absorbance tests have stood the test of time

For decades, single-analyte assays performed in 96-well microplates to produce a colorimetric readout have been the most popular ELISA format. This is largely because they are relatively simple to configure and can be measured using instrumentation and reagents that are already present in the lab. However, these types of assays have their limitations. “Many researchers do not realize that absorbance assays typically offer the least sensitivity and assay performance, and that better technologies are available,” reports Michael Bjerke, Sr. Product Manager at Promega Corporation. “Notably, technologies centered on fluorescence and luminescence open up new assay possibilities that cannot be accomplished with absorbance-based methods.”

Features to consider in an ELISA plate reader

If you are planning to purchase a new ELISA plate reader, there are plenty of options to choose from. To help guide your decision, it is worth investigating the following instrument features.

Sensitivity and dynamic range

Sensitivity and dynamic range are two of the key performance metrics used to describe an ELISA plate reader’s capabilities. Of these, sensitivity refers to how little of an analyte can be accurately detected, and is determined by both the instrument and the assay being used. “A sensitive instrument when combined with a sensitive assay can detect extremely low concentrations of an analyte in a sample,” explains Joy De Torres, Applications Scientist at Azure Biosystems. “In practical terms, high sensitivity can mean the discovery of a scarce analyte in sample material or can provide early detection of a disease biomarker.”

Dynamic range instead relates to the breadth of measurements possible with a particular optical mode. “Because you can’t always predict which experimental samples will result in high or low signals within your assay plate, a wide linear dynamic range is important to be able to efficiently measure both signal extremes,” notes Bjerke. Echoing this point, Eric Matthews, Vice President of Sales, North America, at BMG Labtech, adds that ELISA plate readers fitted with dynamic range extending capabilities can save researchers’ time by removing the need to dilute samples or perform repeat testing of high-concentration wells.

Multimode capability

Multimode ELISA plate readers allow for several different types of measurements to be recorded on a single instrument. “If there is a need to utilize absorbent, fluorescent, and luminescence-based assay technologies then having a multimode reader saves space and cost versus having several independent instruments,” comments Peter J. Brescia, Jr, Applications Scientist at Agilent Technologies. “In addition, multimode readers eliminate the need to move assays that generate more than one type of readout from one instrument to another, which can introduce additional sources of variability and increase the risk of plates being accidentally dropped.”

“In a setting where absorbance ELISA is the only potential use case, and the project has a limited duration, it’s a waste of capital budget to invest in more modes than are going to be used,” says Matthews. “But if a lab may try new methods in the future and plans to use a reader for an undefined number of research projects—which is more often the case—users almost never regret buying a multimode instrument. Once you have the capacity to detect readouts other than absorbance, you will soon find ways of introducing those readouts into your research.”

Ease of use

Ease of use is a critical factor to consider when choosing an ELISA plate reader as it can impact workflow efficiencies. “Being able to get an instrument up and running with minimal training is key to avoiding unnecessary delays to your research,” says Brescia. “Often, further training to allow the use of advanced features will be reserved for superusers or lab staff/managers on an as-needed basis.” Having an intuitive system is also central to ensuring data accuracy. “By reducing the risk of operator errors, a user-friendly instrument can greatly improve the quality and reproducibility of experimental results,” notes De Torres.

Increasingly, the term ‘automatic’ is used to infer ease of use, but Bjerke cautions researchers to find out what this means in practical terms. “Many ELISA plate readers offer an automatic gain adjustment feature to optimize the detector based on the signal intensity range coming from the assay wells,” he explains. “However, on most plate readers, this feature actually requires some degree of user intervention to function properly. In contrast, GloMax^® readers include a true auto-gain adjustment for every sample, such that no manual intervention is required.”

Integrated data analysis

Integrated data analysis eliminates the need to manually transfer data from the ELISA plate reader, meaning a more streamlined workflow, faster time to results, and less chance of mistakes being made. In certain cases, such as with GMP labs, on-board data analysis may even be mandatory. “With an ELISA, users typically want to see the determined concentration of their analyte based upon the values of a standard curve,” explains Matthews. “Integrated data analysis software means they can obtain this data as soon as the test has completed, freeing up their time to be spent on other tasks.”

Compatibility with automation

Compatibility with automation can be important for labs where higher throughput is required. “Instruments used with automation are typically faster and more flexible as they are more difficult to modify once installed,” says Brescia. “This is one area where multimode readers shine given the wide breadth of assays that can be performed. However, in some instances where a specific assay is run in mass then a dedicated single mode reader may be a viable option. In either case, a high-performance, automation capable reader is generally preferred for throughput.”

Additional points

Besides all of the factors just mentioned, you will also want to think about plate format and cost when choosing an ELISA plate reader. “Overall, the importance of different features on an ELISA plate reader will depend on the specific needs of the experiment(s) most frequently performed by the lab,” says De Torres. Additionally, you will want to find out from the instrument manufacturer what level of support you can expect to receive moving forward. “Technical support is a critical factor when choosing any instrument,” advises Bjerke. “All you want is for your assay to work and produce results, but issues can always occur. A strong technical support team can quickly and accurately diagnose the problem and help you to resolve it, keeping your project on track.”