A specific and sensitive ELISA for measuring S-100b in cerebrospinal fluid

Area of Science:

• Biochemistry
• Immunology
• Clinical Chemistry

Background:

• S-100b is a protein found in cerebrospinal fluid (CSF).
• Elevated S-100b levels are associated with various neurological conditions.
• A sensitive and specific assay is needed for accurate S-100b quantification in CSF.

Purpose of the Study:

• To develop and validate a sensitive, simple, and specific sandwich ELISA for quantifying S-100b in human CSF.
• To assess the diagnostic utility of CSF S-100b levels in patients with neurological diseases.

Main Methods:

• A sandwich ELISA was developed using a monoclonal anti-S-100b capture antibody and a horseradish peroxidase-labeled polyclonal anti-S-100b detector antibody.
• The assay was validated for sensitivity, specificity, precision, and recovery using S-100b standards and spiked CSF samples.
• 154 CSF samples from patients with various neurological conditions and controls were analyzed.

Main Results:

• The ELISA demonstrated a lower limit of detection of 0.04 ng/ml with minimal cross-reactivity (<0.006%) with S-100a.
• The assay showed good precision (within-batch CV 5.6-9.3%, between-batch CV 8.1-8.9%) and recovery (94%).
• Elevated CSF S-100b levels (>0.4 ng/ml) were found in 19% of samples, with the highest concentrations in patients with cerebral hemorrhage or CNS malignancy.

Conclusions:

• The developed sandwich ELISA is a reliable and efficient method for routine S-100b measurement in clinical laboratories.
• CSF S-100b levels can serve as a potential biomarker for detecting and monitoring neurological diseases, particularly cerebral hemorrhage and CNS malignancy.
• S-100b appears to be rapidly cleared from CSF, as evidenced by a dramatic decline in levels in a patient with an infected shunt.