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Fee for service
The CHOP TCL "Immunoassay Center" performs >50,000 immunoassays (analyte x sample) annually for the quantitation of protein/peptide biomarkers, cytokines, hormones, and antibodies in various body fluids. In addition to the testing service, TCL also assists in the overall design of the clinical studies and 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 other similar services, we include controls to ensure each assay run meets our stringent quality control standards. For long-term studies requiring multiple batches of testing, the Core will perform lot-to-lot kit comparison so that test data from different batches are comparable.
When choosing an assay platform consider sensitivity, reporting range, cost, turnaround time, and feasibility of lot-to-lot kit comparison/bridging.
The enzyme-linked immunosorbent assay (ELISA) is the most commonly used platform for quantitative protein analysis. It typically uses a 96-well plate and each sample is run in duplicates; each kit can therefore run ~37 samples plus standards and controls.
We can perform any assay as long as a kit is commercially available. Assays from R&D, Millipore and Alpco are generally preferred. Kit prices are normally $300-$1000 (average $600).
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/reporting 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). MSD can therefore 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. We typically use the V-plex or V-plex PLUS assay kits for high quality and consistency.
Compared with MSD, Luminex is more robust in multiplexing (able to run up to 100 analytes using 25 uL specimen), assays are highly customizable (MSD V-plex kits have fixed analytes in one kit), but are generally less sensitive than the MSD V-plex assays. The two systems have their unique assays, so whether Luminex or MSD will be used depends on the set of analytes of a project.
This is an automated immunoassay system developed by Roche 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 low (~$16 per sample, including kit cost) but the tests are limited to clinical assays only.
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 therefore has significantly increased thoughput and lower labor charge than MSD.
The Ella assays are currently for Research Use Only (RUO); therefore, Ella has wider assay selection compared with Cobas e411, 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 ~$7.50 per sample on Cobas e411 but requires 150 uL of samples. ELISA can be used for a smaller amount of samples (~75 uL is needed) and the cost will be ~$20 depending on the number of samples. Insulin is unstable even when frozen, and thus requires 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 now requires 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 consult with Dr. Ren when choosing an appropriate immunoassay.
Small immunoassay projects (< 200 analyte x sample) are typically completed within 1-3 weeks after the TCL receives both the samples and kits. However, turnaround time may be longer if your project is larger or there is a significant ongoing project. Automated systems (Ella and Cobas) have a much faster turnaround time (the capacity can be as high as 700 samples per day).
Please email the TranslationalCoreLab@email.chop.edu for the Sample Submission Form in Excel format.
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Translational Core Laboratories (CHOP)