How is the lot specific code or factor for each EliA batch determined?
The lot specific code for each EliA batch that is used to calculate the final concentration of the test (in IU/ml, U/ml, Ratio etc) is determined at the end of the internal Quality Control procedure for the release of the newly produced EliA Well batch.
In this QC test, amongst other results, the concentration of several predefined positive and negative Quality Control samples and the EliA Positive Control for this test is determined. For each positive sample a target value and a target range is predefined. For the negative samples a threshold level (maximum concentration) is specified. The samples are not only tested on the new batch but also on a reference batch.
Within certain limits the factor is adjusted to best fit the combination of these different specifications on the positive and negative samples in comparison to the absolute targets and to the reference batch results. If the factor cannot be adjusted to fit one of the specifications (for example, the positive samples do not fit inside the concentration range without the blood donors being inside the maximum value) this batch cannot be released.
The factor is needed to minimize the impact of biological, chemical, biochemical variances of the coating processes on the concentration results.
The limitation of the factor selection is that the factor has to be higher than a certain minimum factor. This minimum factor cannot fall below this minimum because otherwise the upper limit of the measuring range given in the DfU would not be valid anymore. This minimum is defined during the tests development & validation by allowing a 20% decrease of the factor from the so called master factor determined during development. The master factor is the factor used to release the validation batches (for the product validation studies) and it is the aim of the production of subsequent batches to always stay as close as possible to this master factor.
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