Can I still use an ELISA Plate if desiccant is not the original blue color?

An ELISA plate should only be used if the desiccant inside the plate pouch is blue. A pink desiccant indicates that moisture has somehow entered the pate pouch, and this could affect results. To properly store an opened plate pouch to minimize this, follow the instructions listed in the packing insert listed under “Storage Conditions”.

What does AAU/mL stand for when utilizing a semi-quantitative assay? How does this correlate with International Units or Units of other test systems?

AAU/mL is a unit value that can be utilized in semi-quantitative ELISA tests. This is calcu-lated by multiplying the OD of the test specimen in question by the unit value of the calibrator for the test kit being used. This number is then divided by the mean OD of the calibrator. AAU/mL has not been calibrated against the Wo/80 standard, and is therefore an arbitrary unit. The dsDNA ELISA kit is the only one that has been calibrated against the Wo/80 standard, and is therefore expressed as IU/mL.

How lenient are incubation times? What result differences can I expect if I acci-dentally go over?

Test System performance has been optimized for the incubation time frames provided in the package insert of the assay you are performing. An assay procedure includes multiple incubation steps, please note that there should be consistency between the incubation times. Therefore, the all subsequent incubation times should be equal to the original. Performance characteristics have not been established for increased or decreased incubation times from what is instructed in the package insert & as a result, precision may vary.

Why do different lots for the same test system contain different CF’s? Should I be concerned if there is a large difference between kit lots?

Different lots of kits will have different CF’s. The CF corrects for any variation due to changes in laboratory temp, different technicians running the tests, etc. There should be no concern if lots have different CFs, even if the difference is large. Samples will produce expected results regardless of the differences in CF. During the manufacturing of an ELISA kit, there are different variables that the technician must account for. Such variables include different lab temperatures, different technicians, different raw materials, such as plate lot, antigen lot, buffer lots, etc. The CF will vary to accommodate these variables yet still assure that the final outcome of the kit is consistent from lot-to -lot.

How strictly must temperature requirements be enforced? Can I leave reagents out at room temperature all day and then return to storage requirements at the end of the day?

All reagents should be returned to their original vials & storage conditions immediately after use. To insure that assay performance and reproducibility is optimal, these guidelines should be followed. Failure to do so can lead to performance variance.

What should I do if I receive an equivocal result?

If a sample generates an equivocal result, it should be repeated in duplicate. Alternatively, the sample could be repeated using another methodology. Please refer to the instructions in the package insert.

Can I utilize left over reagents of one lot on a second lot or are they lot specific?

Reagents should not be used with a new kit once the kit they came in has been depleted. Each kit should be opened and used with its own, fresh reagents. However, while multi-batching or automating multiple ELISA kits together on the same plate, the TMB substrate, Stop Solution and wash buffer can be used as universal components. Additionally, IgG diluents can be used universally with all IgG kits.

I by mistake washed strips I didn’t use…can I still use those strips next time?

Once strips are washed, they cannot be used again for testing. This could potentially affect results.

I put the wrong correction factor in my reader and threw out the plate before I could re-read it, do I need to re-run my test?

This depends on the specific ELISA reader used in each laboratory. Some readers store the OD values read from the plate, and provide the opportunity to input another correction factor and re-generate results. Other readers require that the plate be read again. Please check with the manufacturer of your particular ELISA plate reader. In addition, if your printout has the raw OD values, the results can be calculated manually. Please refer to the package insert of your kit for instructions on how to perform the calculations manually. Follow “Quality Control” and “Interpretation of Results” to obtain your results manually.

Which assays are considered “exceptions”?

Most ZEUS ELISA kits follow a consistent format and procedure but some of them do not and are considered exceptions. ANA Screen has longer incubations, Cardiolipin kits have a different wash buffer, ENA Screen has different plate setup, Lyme IgM has an additional dilution step.

Why do my ODs vary from run to run and how significant is this variation with re-spect to results?

OD (or optical density) or absorbance values are a direct measure of color intensity by an ELISA reader or spectrophotometer. Color development (therefore ODs) during assay processing may change from run to run (even within the same kit lot) due to room temperature fluctuations, incubation time, pipetting, plate washing and tech to tech variability. As long as the Quality Control criteria listed in the package insert are met, the CF (or calibrator correction factor) will accommodate for OD variability when calculating index ratios and interpretive results.