3.4.3 Biological variability over time
For six individuals, results were available of the MSD multiplex immunoassay from a previous blood sampling and testing, in Spring instead of Summer, one year and three months earlier (Table 4). In the prior measurements, plasma samples were used, while in the current tests, serum samples were analysed. However, previously analysis of serum and plasma samples collected at the same time showed a correlation of r =0.92 (P<0.001), indicating that both matrices show comparable sIgE-levels with the MSD multiplex immunoassay. The biological variation over time was observed to be consistent (r =0.94-1; P<0.001). The correlation for subject 13 was, however, lower (r =0.65; P<0.05), which was most probably due to seasonal effects (sampling time Spring vs. Summer).