Comparison of three assays for quantifying S-100B in serum

Background: Serum S-100B has clinical value in monitoring malignant melanoma and in monitoring and predicting outcomes in patients with traumatic brain injury.

Methods: Analytical performance characteristic and split-sample method comparison studies for three commercial S-100B immunoassays (CanAg® S100, Sangtec® 100, YK150 Human S-100 β) were performed. Reference intervals (97.5th percentile) for each assay were established by non-parametric analysis of results from healthy volunteers.

Results: Linearity results were slope=1.014, intercept=65.1, r(2)=0.999 for the Sangtec assay; slope=1.038, intercept=31.1, r(2)=0.999 for the CanAg assay; slope=1.123, intercept=-105.4, r(2)=0.997 for the YK150 assay. Within-run CVs were ≤5.7, ≤6.3 and ≤10.8 for the Sangtec, CanAg and YK150 ELISAs, respectively. Between-run CVs were ≤11.3, ≤5.9 and ≤9.5, respectively. Upper reference interval limits of 141, 96 and 735 ng/l S-100B were established for the Sangtec, CanAg and YK150 ELISAs, respectively. Deming regression generated the following: CanAg vs. Sangtec, slope=0.339, intercept=24.1, r(2)=0.932; YK150 vs. Sangtec, slope=0.266, intercept=-140.0, r(2)=0.690; YK150 vs. CanAg, slope=1.376, intercept=-13.1, r(2)=0.860.

Conclusions: The configurations, procedures and performance characteristics of the Sangtec and CanAg S-100B ELISAs are comparable and better than those of the YK150 assay. Poor agreement and large biases prevent interchangeable use of results.