DESCRIPTION

S100B is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs and has been implicated in the regulation of cellular activities such as metabolism, motility and proliferation. S100B is highly expressed in astrocytes in the brain. It is also expressed in the Schwann cells of the peripheral nervous system, and outside the nervous system in melanocytes, adipocytes and chondrocyte. Elevated S100B levels in cerebrospinal fluid and serum reported after head trauma, subarachnoid hemorrhage, and stroke were correlated with the extent of brain damage. An association between elevated serum S100B and the presence of brain metastases has been reported. Increased S100B levels may also be found in patients with cerebral small vessel disease (SVD).

PRINCIPLE OF THE ASSAY

An anti-tag antibody is pre-coated onto the bottom of wells. After adding antigen or samples, Tagged-Capture antibody and HRP-conjugated detection antibody, a sandwich complex is formed in the solution. TMB acts as a HRP substrate, and the solution color will change from colorless to blue. A stop solution containing sulfuric acid turns the solution yellow. The color intensity is proportional to the quantity of bound protein, which is measurable at 450 nm with the correction wavelength set at 630 nm.

PRECISION

Intra-assay Precision (Precision within an assay) Three samples of known concentration were tested 8 times on one plate to assess intra-assay precision. Inter-assay Precision (Precision between assays) Three samples of known concentration were tested in 16 separate assays to assess inter-assay precision.

Intra-assay Precision

Sample	n	Mean (ng/mL)	SD	CV%
1	8	7.98	0.19	2.38
2	8	2.01	0.08	3.98
3	8	0.61	0.04	6.56

Inter-assay Precision

Sample	n	Mean (ng/mL)	SD	CV%
1	16	7.91	0.22	2.78
2	16	2.01	0.08	3.98
3	16	0.60	0.04	6.67

RECOVERY

The recovery of human/mouse/rat S100B spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average% of Expected	Range (%)
Tissue lysate	1:16,000	107	105-110
	1:32,000	106	104-109
Human cerebrospinal fluid (CSF)	1:16	113	110-115
	1:32	111	109-112

LINEARITY

To assess the linearity of the assay, samples were diluted with the appropriate Sample Diluent to produce samples with values within the dynamic range of the assay. (The tissue lysate was initially diluted 1:16,000. The human cerebrospinal fluid (CSF) was initially diluted 1:2.)

		Tissue lysate	Human cerebrospinal fluid (CSF)
1:2	Average% of Expected	100	100
	Range (%)	-	-
1:4	Average% of Expected	83	105
	Range (%)	82-84	104-106
1:8	Average% of Expected	78	106
	Range (%)	73-82	105-107
1:16	Average% of Expected	86	102
	Range (%)	84-88	101-104

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human/mouse/rat S100B produced at Sunlong Medical™.