DESCRIPTION

Chitinase 3-like-1 (CHI3L1/YKL-40/CGP-39/GP-39/hCGP-39) is a protein secreted from restricted cell types including colonic epithelial cells (CECs) and macrophages. CHI3L1 is an inflammation-associated molecule, and its expression is enhanced in persons with colitis and colon cancer. CHI3L1 is a 40 kDa protein and is produced by restricted cell types, including colonic epithelial cells (CECs) and macrophages. CHI3L1 can be detected in the Golgi apparatus and the endoplasmic reticulum, but its major sites of action seems to be extracellular as a secreted protein.

PRINCIPLE OF THE ASSAY

Sandwich ELISA structure (Detection antibody labeled with biotin) A capture antibody is pre-coated onto the bottom of wells which binds to analyte of interest. A detection antibody labeled with biotin also binds to the analyte. Streptavidin-HRP binds to the biotin. TMB acts as the HRP substrate and the solution color will change from colorless to blue. A stop solution containing sulfuric acid turns 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 20 times on one plate to assess intra-assay precision. Inter-assay Precision (Precision between assays) Three samples of known concentration were tested in 24 separate assays to assess inter-assay precision.

Intra-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	20	989.82	24.78	2.5
2	20	239.03	8.27	3.5
3	20	67.01	2.07	3.1

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	24	1,086.40	20.08	1.9
2	24	279.98	5.31	1.9
3	24	71.30	3.63	5.1

RECOVERY

The recovery of human CHI3L1/YKL40 spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average% of Expected	Range (%)
Human serum	1:160	88	84-92
	1:320	90	81-105
Cell culture supernatant	1:8	85	83-88
	1:16	89	85-93
Urine	1:8	92	79-101
	1:16	94	86-102

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 cell culture supernatant samples were initially diluted 1:4. The human serum and plasma samples were initially diluted 1:40. The urine samples were initially diluted 1:4.)

		Human serum	Human plasma	Cell culturesupernatant	Urine
1:2	Average% of Expected	100	100	100	100
	Range (%)	-	-	-	-
1:4	Average% of Expected	99	98	112	113
	Range (%)	88-108	97-98	109-117	109-118
1:8	Average% of Expected	100	101	118	116
	Range (%)	96-103	100-102	112-125	110-118
1:16	Average% of Expected	102	108	96
	Range (%)	97-113	105-111	84-108

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human Human CHI3L1/YKL40 Sandwich ELISA Kit produced at Sunlong Medical™.