Why are the detection limits of our EliA tests so different although it is always the same curve?
The detection limit of all EliA IgG tests is 600 µg/l as this is the highest calibration point. However, we do not give results in µg/l but in Units/ml and, thus, every limit is multiplied with the individual lot-specific factors. How this calculation is done in IDM, please see Calculation of EliA Units ».
In our DfUs we give a minimum upper limit, specific per test. This value was calculated with the lowest lot-specific-factor, which is possible with this test. In most cases it is higher (that is why we give the upper limit of the measuring range with a ">"-sign). Please find the minimum measuring ranges given in the EliA DfUs. (see further explanation on the limit here)
Of course, the fluorometer is able to measure higher RU-values than that of the highest calibration curve. The fluorometer measures 4-MUF in concentrations between 6.7 nM – 54 uM. This leads to signals between approximately 0.3 mV – 1900 mV or, expressed in RU, 7.5 RU – 47500 RU.
However, as the curve is not a line but a curve with an S-shape, the values above the highest calibration point are not valid. If a sample is "above" it could be diluted until it is in the measuring range. However, for autoimmune sera this is not recommended, because they often do not dilute linearly (see linearity »).
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