IDS IDS-iSYS, User Manual

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1-5-3- Immunoassays
Assays are carried out using either a one-site or two-site method.
One-site (competitive) method assay
The assay is based on competition between an unknown quantity of analyte in a sample with the labelled
analyte in the kit.
In a sample where no analyte is present, maximum binding of the labelled analyte is possible. With the
increasing analyte concentrations, decreasing binding of labelled analyte is observed.
The signal generated by the labelled analyte in the luminometer is therefore inversely proportional to the
concentration of analyte in the sample.
Two-site (sandwich) method assay
This technique uses two antibodies that detect and bind di ff erent portions of the analyte molecule. Incubation
of these antibodies with the sample results in the formation of a ‘sandwich’ complex, where the analyte is
specifically bound by both antibodies. Incubation with coated magnetic particles allows capture of these
complexes.
For chemilumescence assays, after washing, the cuvette is transferred to luminometer where trigger solutions
are injected into the reaction cuvette. For enzyme-luminescence detection assays, after washing, the substrate
is added into the cuvette then transferred to the luminometer.
For enzymatic assays, after washing, the substrate is added into the reaction cuvette where the reaction takes
place. Increases in absorbancy are monitored by the spectrophotometer.
The signal generated by detection of the captured complexes is directly proportional to the concentration of
analyte in the sample.
Calculation of results
The results are calculated in comparison to a calibration curve.
The specific reference curve (master curve) for a reagent lot is in the file containing all the data for that lot, that
is provided on the CD accompanying the cartridge. This information is registered in the analyser’s database
when the CD is introduced on the controlling computer.
If a new reagent lot is used, this curve must be registered on the database and then adjusted by a 2 point
calibration before sample results can be calculated.
2 point calibration
Analyser-to-analyser variation and di ff erent reagent lots will require adjustment of the master curve
(calibration). This is done by assaying two calibrators supplied with the reagent cartridge. The analyser’s
software will automatically perform the data processing to generate a new curve by defining new values for
two of the four parameters considered to be critical.
In practice, the 4 parameters of the reference curve specific to the reagent cartridge lot are loaded in the user’s
analyser via a CD provided with the kit. Calibration of the test must then be requested prior to use. The
calibration is performed and then verified by assaying one or more controls. Subsequent calibrations must be
repeated regularly in accordance with each assay’s instructions for use or as prompted by the analyser.
Operating principle
1-5- Operating principles (continued)
IDS-iSYS User Manual - Revision M1
Operating principle 1-5
13
Software version V 14