A Brain-derived Neurotropic Factor (BDNF) Immunoassay Able to Quantitate Both Increased and Decreased BDNF Levels over the Course of Disease
A client needed to measure fluctuations in BDNF levels with LBA, both increased and decreased BDNF levels, in human sera as a measure of pharmacodynamics (PD) associated with their drug candidate. Mature BDNF is present in normal serum at ~25 ng/mL and it was desired to have a lower limit of quantitation (LLOQ) of ~5-8 ng/mL. Regulatory guidance dictates that the assay is conducted in the same matrix as the test samples, in this case human serum. Quantitating low levels of BDNF would require a surrogate matrix because of relatively high endogenous BDNF content in normal human serum.
The challenge was to design a surrogate matrix that would be scientifically justified and allow for quantitation of BDNF at low ng/mL levels in patient sera.
It was known that most mature BDNF in sera samples is derived from platelets. Platelet-poor plasma was prepared (i.e., low BDNF) and converted to serum by addition of excess calcium. The BDNF-poor serum proved a highly appropriate and suitable surrogate to authentic serum in this BDNF LBA prepared by the normal clotting mechanism. Our study on this issue can be seen here.