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).