Plasma-based S100B testing for management of traumatic brain injury in emergency setting.

BACKGROUND: Serum biomarker S100B has been explored for its potential benefit to improve clinical decision-making in the management of patients suffering from traumatic brain injury (TBI), especially as a pre-head computed-tomography screening test for patients with mild TBI. Although being already included into some guidelines, its implementation into standard care is still lacking. This might be explained by a turnaround time (TAT) too long for serum S100B to be used in clinical decision-making in emergency settings. METHODS: S100B concentrations were determined in 136 matching pairs of serum and lithium heparin blood samples. The concordance of the test results was assessed by linear regression, Passing Pablok regression and Bland-Altman analysis. Bias and within- and between-run imprecision were determined by a 5 × 4 model using pooled patient samples. CT scans were performed as clinically indicated. RESULTS: Overall, S100B levels between both blood constituents correlated very well. The suitability of S100B testing from plasma was verified according to ISO15189 requirements. Using a cut-off of 0.105 ng/ml, a sensitivity and negative predictive value of 100% were obtained for identifying patients with pathologic CT scans. Importantly, plasma-based testing reduced the TAT to 26 min allowing for quicker clinical decision-making. The clinical utility of integrating S100B in TBI management is highlighted by two case reports. CONCLUSIONS: Plasma-based S100B testing compares favorably with serum-based testing, substantially reducing processing times as the prerequisite for integrating S100B level into management of TBI patients. The proposed new clinical decision algorithm for TBI management needs to be validated in further prospective large-scale studies.

Reference change values of M-protein, free light chain and immunoglobulins in monoclonal gammopathy.

OBJECTIVES: Clinical decisions in patients with monoclonal gammopathies may be highly imprecise because of variations of parameters used in diagnosis. In this study, we aimed to calculate the variation in M-protein, free light chains (FLCs), and immunoglobulins in respective patients. DESIGN & METHODS: We analyzed the data of clinically stable patients with monoclonal gammopathy (MG), which were monitored for 7-years to determine the biological variations and reference change values (RCV) of serum M-protein, monoclonal serum FLCs and immunoglobulin (Ig) concentrations. Patients that were included in the study had no change in diagnosis and showed <5 g/L change in serum M-protein during the monitoring. From the patients included at least 3 consecutive samples were analyzed within 8 months and 7 years of initial diagnosis. RESULTS: The total coefficient of variations (CV) was calculated for M-protein and involved/uninvolved fractions of FLCs and immunoglobulins. From 38 patients and 456 samples that were included in the study, the total CVs were calculated for serial M-proteins (8.9%), serum involved FLCs (iFLC, 21.4%), involved Ig (i-Ig, 8.7%) and uninvolved Ig (u-Ig, 9.1%). Combining these CVs and the interassay analytical CVs, we calculated the biological CV for the serum M-protein (8.4%), serum iFLC concentration (21.1%), i-Ig (8.6%) and u-Ig (9.0%). A significant correlation was found in multiple myeloma patients between the κ/λ light chain ratio (rFLC) with i-Ig, the difference between i-Ig level and u-Ig level (d-Ig) and ratio Ig (r-Ig) (r = 0.790, 0.703 and 0.711, respectively). These correlations were not found in patients suffering from MG of undetermined significance and smoldering multiple myeloma. CONCLUSIONS: i-Ig determinations may be an alternative to M-protein for MGs. The variations in serum FLC measurements during MG monitoring were greater than those observed in serum M-proteins and therefore need to be more rigorously revised for recommendations.