The manufacture of Freelite assays follows established validated protocols. Each batch of reagents undergoes rigorous testing to ensure the quality of the kit components (Figure 5.8)
. Once the latex and supplementary reagent has been manufactured, the precision and linearity of the assay is tested. Next, a value is assigned to the kit calibrators using the Internal Reference standard. This is achieved using 100 separate assays and 10 separate calibration curves. Values are assigned to control samples using similar protocols.
For each new batch of antisera, specificity is controlled by comparing sFLC results for panels of samples with results from previous batches. The panel samples include normal sera and patient sera containing polyclonal or monoclonal sFLCs (typically from multiple myeloma patients). The results are compared using Passing-Bablok analysis and are considered acceptable when they fall within a defined set of criteria. Typical batch-to-batch comparison data is shown in Figure 5.9
Analytical comparisons are also made using a large number of normal sera. A typical evaluation of a panel of 90 normal samples on the Binding Site SPAPLUS produced the following results: mean κ = 8.86 mg/L (range 4.32 - 20.6 mg/L), mean λ = 11.85 mg/L (range 3.77 - 28.77 mg/L). Freelite normal ranges are further discussed in Chapter 6. Once a final pre-packaging test is complete, the kit is packaged ready for release.