Assays and Risk Assessment

1 Qualitative Versus Quasi-Quantitative LBA Assay Formats 

It is a regulatory expectation that the sensitivity of the assay will be determined in concentration units, (i.e., ng/mL). Thus, an approximate concentration of antibody can 

2 Qualitative Versus Quasi-Quantitative Nab Assay Formats 

Alternatively, results may be reported as the amount of semm required to neutralize the biological activity induced by a constant amount of the antigen [40]. For example, for GM-CSF, the volume of semm required to neutralize the activity of 10IU of cytokine can be calculated using semm ED50 responses obtained by fitting common asymptotes and slope for all sera analyzed. This approach can also be used to analyze responses to different GM-CSF preparations/products and can be applied to other biologicals. 

One of the difficult issues associated with assays for antibody detection is the interpretation and evaluation of the results obtained. The usual approach for evaluation of antibodies is firstly the classification of the sample as positive or negative for antibodies in a preliminary screening assay followed by confirmation of positives, and secondly a careful and thorough quantitation of the amounts of antibodies (if present) in the relevant biological sample and further characterization by testing for 

---