Immunoassays

The CHOP TCL performs > 50,000 immunoassays (analyte x sample) anually for the quantitation of protein/peptide biomarkers, hormones, and antibodies in various body fluids. In addition to the testing service, TCL also provides assistance in the overall design of the clinical studies & trials with regard to the sample type and volume requirements, sample collection guidance, storage time (analyte stability), assay platform selection, and the need for assay validation and lot-to-lot comparison. Unlike many others, we include controls in every run of our assays to ensure that each assay meets our stringent quality control standards. For long term studies that require multiple batches of testing, lot-to-lot kit comparison will be performed so that the test data from different batches are comparable.

Choosing the right assay platform - consider sensitivity/reportable range, cost and turnaround time.

ELISA

The enzyme linked immunosorbent assays (ELISA) is the most commonly used platform for quantitative protein analysis. It usually uses a 96-well plate and each sample is run in duplicates, thus each kit can run ~37 samples plus standards and controls.  We can perform any assay as long as there is a commercially available kit.  Assays from Alpco, R&D and Millipore are generally preferred.  Kit prices are normally $300-$1000 (average $600).  Our testing fee is ~$6.00.  We also perform assay development and validation when commercial kits are not available.

MSD

The Meso Scale Discovery (MSD) platform uses electrically activated chemiluminescence rather than enzyme based color development as the means for detection.  This significantly improves signal-to-noise ratio, resulting in higher sensitivity and wider dynamic range.  It also allows multiplex analysis which means two or more analytes can be tested in one well (ELISA can only detect a single analyte per well).  Thus MSD can be considered a more "advanced ELISA", and is currently the preferred immunoassay system in the pharmaceutical research field.  The overall cost to the investigator is also lower than ELISA. MSD's multiplex assays have much higher sensitivity and broader range than the Luminex panels. Click here for options of multiplex assays.

Immulite 1000

This is an automated immuno-chemiluminescent assay system developed by Siemens for in vitro diagnostics (IVD) purpose.  Unlike ELISA and MSD, samples are often directly loaded to the instrument and the test is performed automatically with minimal hands-on operation. The major disadvantage is that it may require higher sample volume (0.15 ml or more).  The overall cost to the investigator is very low (~$14 per sample including kit cost) but the tests are limited to clinical assays only.

Ella

Ella is an automated immunoassay system using a combination of microfluidics and immunofluorescence technologies.  Compared with ELISA, Ella has increased sensitivity, wider dynamic range, minimum sample consumption, lower cost, faster turnaround time, and multiplex capability.  These traits are similar to MSD.  However, Ella is automated thus it has significantly increased thoughput and lower labor charge than MSD.  The Ella assays are currently for Research Use Only (RUO) thus Ella has wider assay selection compared with Immulite which is limited to clinically relevant assays.  Ella is co-developed by ProteinSimple and R&D in a way that R&D provides the same antibody-pairs in their Quantikine kits, and test results correlate with each other.

Which Assay Platform Should I Use?

The above immunoassay platforms offer different technical advantages at different costs.  They may also differ in sample requirements (type, volume and storage).  Some assays can be done in a multiplex fashion to reduce cost and sample consumption. Take insulin as an example, the price is $6 per sample on Immulite but requires 400 uL of samples.  ELISA can be used if you have smaller amount of samples (~75 uL is needed) and the cost will be $7.35-$12.88 depending on the number of samples.  Insulin is unstable even when frozen, and thus require frequent testing (every 3-6 months).  To ensure the data are comparable over different batches of testing, we perform lot-bridging (lot-to-lot comparison) for insulin at no extra cost to our PIs. This is critical to a long term project and NIH is now demanding such lot-bridging measures as part of the "authentication requirements".  Without lot bridging, you may not be able to publish your data.  Additionally, there are multiplex testing options for insulin on the MSD system.  Therefore investigators (especially junior investigators) are highly encouraged to have discussions with Dr. Ren when choosing an appropriate immunoassay.

Turn Aound Time

Small immunoassay projects (< 200 analyte x sample) can be typicaly completed within 1-3 weeks after we receive both the samples and the kits. However turnaround time may be significantly longer if you have a bigger project or there is a big ongoing project.  Automated systems (Ella and Immulite) will have a much faster turnaround time (the capacity can be as high as 700 samples per day).

Please email TranslationalCoreLab@email.chop.edu for the Sample Submission Form in Excel format.