Validation and Comparison of Two Solid-Phase Immunoassays for the Quantification of S-100B in Human Blood

Abstract

S-100 protein concentrations in serum are considered a quantitative marker of the extent of damage to the central nervous system (CNS) (1)(2)(3), including possible cerebral injury following procedures such as coronary artery bypass surgery (4)(5). There are 19 S-100 proteins, of which S-100A1 and S-100B are the most prevalent (6). S-100A1 and S-100B form dimeric proteins that previously were labeled S-100a (S-100A1-B), S-100b (S-100B-B), and S-100a (S-100A1-A1) (7)(8)(9). Initial studies of S-100 protein reported that this protein is present only in the CNS (7), but later studies found various concentrations of S-100A1 and S-100B in tissues outside the CNS, including the heart and aorta (10). At present, there are questions about the subtype specificity of S-100 assays, about which subtype of S-100 is associated with different clinical entities, and how the results obtained using various assays compare. To answer these questions, we used the Sangtec 100® LIA and the immunofluorometric (IFMA) S-100 assay to analyze purified recombinant monomeric S-100 proteins, purified dimeric S-100 proteins isolated from bovine brain, and blood samples from patients with various CNS diseases, malignant melanoma, or post cardiac surgery and compared the results. Serum (Sangtec 100 LIA) or heparinized plasma (IFMA S-100) samples were drawn from 218 patients (141 males, 77 females; ages, 16–89 years; mean, 55.4 ± 16.2 years) and 121 healthy blood donors (64 males, 57 females; ages, 18–65 years; mean, 37.8 ± 12.7 years). The study was approved by the local Research Ethics Committee, and all subjects gave informed consent to the procedure. One hundred four of the patients suffered from CNS disease: subarachnoid hemorrhage (n = 41), intracerebral hemorrhage (n = 17), head trauma (n = 19), ischemic cerebral infarction (n = 4), cerebral tumor (n = 12), hydrocephalus (n …