Features of urine S100B and its ability to rule out intracranial hemorrhage in patients with head trauma: a prospective trial.

PURPOSE

Traumatic brain injury causes morbidity and mortality worldwide. S100B is the most documented emergency brain biomarker and its urine-assay might be advantageous because of easier sampling. The primary aim was to evaluate urine S100B's ability to rule out intracranial hemorrhage. Secondary aims included S100B temporal pattern for 48 h post-trauma and chemical properties of urine that affect urine S100B.

METHODS

Patients with head trauma were sampled for serum and urine S100B. Patients who were admitted for intracranial hemorrhage were sampled for 48 h to assess S100B-level, renal function, urine-pH, etc. RESULTS: The negative predictive value of serum S100B was 97.0% [95% confidence interval (CI) 89.5-99.2%] and that of urine S100B was 89.1% (95% CI 85.5-91.9%). The specificity of serum S100B was 34.4% (95% CI 27.7-41.6%) and that of urine was 67.1% (95% CI 59.4-74.1%). Urine-pH correlated strongly with urine S100B during the first 6-h post-trauma. Trend-analysis of receiver operator characteristics of S100B in serum, urine the arithmetic difference between serum and urine S100B showed the largest area under the curve for arithmetic difference, which had a negative predictive value of 93.1% (95% CI 89.1-95.8%) and a specificity of 71.8% (95% CI 64.4-78.4%).

CONCLUSION

This study cannot support ruling out intracranial hemorrhage with urine S100B. Urine-pH might affect urine S100B and merits further studies. Serum and urine S100B have poor concordance and interchangeability. The arithmetic difference had a slightly better area under the curve and can be worth exploring in certain subgroups.