8 criteria for selecting your ELISA kits
Biomarkers specialists are often asked to select an ELISA kit for researchers: with thousands of ELISA references available on the market, the choice can be tricky regarding proteins for which several kits available.
When researchers have to choose a new ELISA kit, the price is regularly the first parameter of selection. But my experience with long term projects shows that it should in fact be the very last one…
Here are some key points to consider first, when selecting the most appropriate immuno-assay kit:
#1- The species studied
When you work on classical models such as Human or Mouse, there shouldn’t be any problem finding a validated kit. Some manufacturers now even provide much more choice such as dog, porcine, monkey… (ex. RayBiotech, Elab Sciences). But when you come to consider a kit validated on species that should show homology with your model, you may appreciate a competition immuno-assay where the single capture antibody will not be as stringent as an antibody pair.
#2- The quality of samples analysed
Although most ELISA kits are validated on serum/plasma and culture supernatants, you should always check the specifications of the kit before collecting your samples, or select the kit according to your own specifications…
As an example, one should check how plasma samples are collected (heparin, EDTA?) before starting to collect all the samples for the sudy and if they are compatible with the assay.
Remember that some conditions may drastically interfere with proper measurement: hemolysis of plasma, presence of lipids in the samples, HAMA effect, fetal calf serum in your cell culture supernatants… Just have a look at our ELISA tips to optimise your results.
If you wish to work on cell/tissue lysates, take into consideration that not so many antibody pairs are able to optimally distinguish their target among the bunch of proteins present in the lysate. Moreover, this “matrix effect” is amplified by the detergents used for the lysis. But don’t panic, once you have a kit validated on lysates, you also get a sample preparation procedure…
#3- the expected concentration of biomarker
If you don’t have a clue about the concentration of your marker of interest in your samples, the assay with the broadest detection range should be preferred. In parallel, multiple dilutions might be made during the validation stages. Single dilutions can only be used in a long term project when you already know the kit and how your samples behave. If you expect your samples to contain very low concentrations of your biomarker(s) of interest, try to keep at least 1/2 dilution in dilution buffer to make your sample close to the standard range and avoid any matrix effect.
#4- the sample size
ELISA kits can require from 100µl down to 10µl for very high sensitivity assays, for each analyte. If you handle very tiny samples, or very precious ones, this should be a key selection criterium. Of course the question get even more critical when you have several proteins to measure. By the way, have you ever considered multiplex assays?
#5- An inter-assay normalization
ELISA kits used in R&D applications are not internationally normalized. The result obtained (reflecting the quantity amounts of biomarker in the samples) is “antibody-dependant”. So, if you want to reproduce the results of a former assay, you have more chances with the exact kit already used. But of course, your assay must be equivalent, especially the quality of your samples…
As a matter of fact, this also true for your own assays over time. And I would recommend that you have an internal control that can be used on all plates to ensure the reproducibility of your tests. This internal control depends on your assay, that’s why it cannot be provided in the research kit as it is in diagnostics assays that have normalized sample preparation procedures.
#6- The experimental protocol
When multiple analytes have to be tested, try to keep the same protocol (and same brand) for all of them. This will avoid much confusion between the assays…
But if you regularly have the same analytes to test, why not consider a multiplex solution?
This would save you time, samples & money. Q-Plex and Quantibody assays will definitely help for any combination of secretome proteins. If you have another range of proteins to analyse, we can take advantage of Quansys’ long-term assay consolidation experience to set a customized kit fitting your project.
#7- The source of the EIA
For some dedicated research domains, you may refer to specialized manufacturers :
- If you want to follow the hormonal activity of big cats or wild monkeys, you may appreciate working on non-invasive samples… Arbor Assays has a unique choice of ELISA kits validated on multiple animal species, optimized to work on urine of feces samples
- Interested in lipids? Echelon has developed a range of ELISAs for S1P, PIP… These ELISA kits have been cited in many international publications. The use of specific patented antibodies is most probably the reason of their undisputed quality.
- Antibody array user? RayBiotech offer ELISA kits produced with the same antibody pairs as their profiling arrays
Interestingly, European distributors in Life Sciences such as tebu-bio, centralize all these specialized manufacturers of immuno-assays in one central place to make your immuno-assay purchases more convenient.
#8- Finally, the budget
Of course, once all technical aspects have been checked, the price of your immuno-assays can be a criterium. But again, this has to be considered in a more global vue:
- Does the delivery program fit with your time-frame?
- For a long-term project: how can you test a kit, and then get identical kits for the rest of your project?
Contact your Biomarker specialist to…
- select the best ELISA for your model,
- get help to build a personalized multiplex assay,
- define a project plan with scheduled test, deliveries, global project cost,
- find outsourcing solution to get the results without the hurdle of the ELISA assay…