PKP-008 Long term stability of trastuzumab in serum samples

BackgroundImmunoassays remain the primary analytical method for quantification of macromolecules such as monoclonal antibodies (mAbs). For the quantification of mAbs in serum or plasma, study samples are not immediately analysed once collected, and thus the various conditions that study samples undergo must be considered to ensure that analytical stability has not been compromised.PurposeTo analyse the long term stability of the monoclonal antibody trastuzumab (Herceptin) in serum samples at -20°C.Material and methodsBlood samples (1.5 mL) were stored in K2EDTA tubes (Becton Dickinson, USA). They were immediately sent to the laboratory, centrifuged (2 × 3000 g/5 min) and were divided into two aliquots. One aliquot was immediately analysed. The second aliquot was stored at −20°C for 2 months and then analysed. The immediately analysed samples were considered the baseline value. At the time of analysis, both samples were analysed at dilutions of 1/20 and 1/80 in duplicate to minimise pipetting errors and the intrinsic variation of the method. Serum trastuzumab concentrations were determined by enzyme linked immunosorbent assay (ELISA) using the automated analyser TRITURUS (Grifols). SPSS statistical (v.22.0.0.0) program was used for statistical analysis. Repeated measurements made from the same samples kept under different storage conditions were tested using the Wilcoxon test. A p value