Greater Q-Plex Sensitivity

If your antigen concentrations are very low, we first recommend that you select a High Sensitivity or SinglePlex Q-Plex™ Array. The assays in these kits have specifically been optimized to have the greatest sensitivity possible.

If you already have a normal kit, you can try the slightly modified protocol and data analysis tips below. Consider changes to the assay protocol carefully, however, as this can also have undesirable side effects. You might also consider requesting a Demo Kit to see if a modified protocol will work with your samples.

Modified Assay Protocol for Increased Sensitivity: Use at your own risk

To optimize for detection at the low end of the curve, extend the standard curve a few extra points, and use longer incubation times, for example:

Spot Position Analyte Average Crosstalk
Spot 1 IL-1a 0.00%
Spot 2 IL-1b 0.06%
Spot 3 IL-2 0.03%
Spot 4 IL-4 0.01%
Spot 5 IL-5 0.00%
Spot 6 IL-6 0.00%
Spot 7 IL-8 0.00%
Spot 8 IL-10 0.00%
Spot 9 IL-12p70 0.00%
Spot 10 IL-13 0.00%
Spot 11 IL-15 0.00%
Spot 12 IL-17 0.09%
Spot 13 IL-23 0.03%
Spot 14 IFNy 0.00%
Spot 15 TNFa 0.04%
Spot 16 TNFb 0.00%

This modified protocol sacrifices some quantitation, 1-2 points, at the top end. Also, some samples may have increased background with longer incubations, which will decrease sensitivity.

Data Analysis Tips

To optimize the curve fit for the low end, first, mask standard curve points if their % backfit is not 80%-120% (shown in the Report tab of Data Analysis). Next, mask the top 2-3 points of the standard curve if they haven’t already been masked. Finally, choose either Auto-Select or Log-Log as the regression model. This may provide a better fit at the low end of the curve.

Can I increase incubation temperatures?

This is not recommended. We find that increasing incubation temperatures can cause antigens to degrade and non-specific binding to increase.

Can I run my samples undiluted? Or less dilute?

This is not recommended for most sample types. Cell culture media is the only sample type that can be tested neat, but all other sample types should be diluted at least 1:2 (50%) for use in Q-Plex™ Arrays. This is because of the increased likelihood of getting false positives and high variability between replicates with neat samples – rheumatoid factors and heterophilic antibodies such as HAMA are usually the culprit in blood-derived samples, while high total protein or lipid content often causes well background problems with tissue-derived samples. Q-Plex™ Array diluents have additives to address these issues. If you are concerned that false positive signals may occur in your samples, test them at several dilutions, such as 1:2, 1:20, and 1:200, and check that the dose-response is linear. Signal from heterophilic antibodies will often not dilute out, while real signal should get dimmer as the sample is diluted.


As researchers and problem solvers ourselves, we understand the value of sound data. We are proud to be a part of research that can better the world. We value the relationships, partnerships, and friendships that we have built with the people who trust and use our technology. We are committed to building these relationships. You can count on us to answer the phone and take time to thoroughly address questions or concerns about any of our products. In an industry that is reputed for grandiose claims, we trust that our quality standards and our customer service set us apart from the competition. If you’re happy with our products or if you think we can do something better, we hope you will let us know.


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