Maintaining batch-to-batch consistency is essential, as sFLC assays may be used for monitoring individual patients over many years. The key component of any nephelometric or turbidimetric immunoassay is the polyclonal antisera. Therefore, it is essential to minimise any change in the composition of the antisera over time.
In order to ensure consistency between production batches of polyclonal antisera, a virtual “rolling pool” of antisera has been established. This pool consists of a list of pre-approved antisera (Section 5.3 explains how suitable antisera are identified). During the manufacture of a batch of reagent, an equal portion of each approved antiserum from the list is mixed. As individual antiserum volumes vary, stocks become exhausted at different times. When this occurs, the antiserum is replenished with a new pre-approved antiserum. The pool of polyclonal antisera used in the manufacture of Freelite assays will always contain at least 90% of the same constituent antisera as the previous batch of reagent. The use of rolling pools of antisera during FLC assay manufacture has minimised batch-to-batch variation whilst ensuring a full range of FLC epitopes are recognised .
Once a pool of suitable polyclonal antisera has been created, the sheep antibodies are attached to latex particles (in order to enhance their performance in nephelometric and turbidimetric immunoassays).