DESCRIPTION

Resistin, a cysteine-rich hormone secreted primarily by rodent fat cells, was postulated to be implicated in obesity, insulin resistance and diabetes. Resistin is also secreted by macrophages in humans, promoting inflammation. Resistin modulates the synthesis and secretion of key pro-inflammatory cytokines such as TNF-α, IL-6 and IL12 in macrophages via a nuclear factor-kB (NF-kB)-dependent pathway. Given the connection between inflammation and cancer, resistin was soon considered for its role in cancer. There were observations supporting its possible use as a diagnostic marker, expression levels of which also seemed to differ in patients with varying clinical stages. Resistin has been also linked to other pathologies such as atherosclerosis.

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 (pg/mL)	SD	CV%
1	8	2,536.7	113.0	4.5
2	8	618.1	27.4	4.4
3	8	263.8	12.9	4.9

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	16	2,431.6	147.8	6.1
2	16	614.7	30.9	5.0
3	16	264.8	12.0	4.5

RECOVERY

The recovery of human Resistin spiked to three different levels throughout the range of the assay in human serum was evaluated.

Sample Type		Average% of Expected	Range (%)
Human serum	1:64	116	110-121
	1:128	113	110-116

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 human serum was initially diluted 1:8.)

		Human serum
1:2	Average% of Expected	100
	Range (%)	-
1:4	Average% of Expected	106
	Range (%)	102-111
1:8	Average% of Expected	107
	Range (%)	106-108
1:16	Average% of Expected	105
	Range (%)	100-111

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human Resistin produced at Sunlong Medical™.