DESCRIPTION

Fibroblast growth factor (FGF)19 is a hormone that regulate metabolic processes particularly during feeding or starvation, thus ultimately influencing energy production. FGF19 is secreted by the intestines during feeding and negatively regulates bile acid synthesis and secretion. FGF19 is regarded as late-acting hormones because its functions are only used after insulin and glucagon have completed their actions. FGF19 shows extensively functional overlap in terms of improving glucose tolerance, insulin sensitivity, weight loss, and lipid, and energy metabolism, particularly in pathological conditions such as diabetes, obesity, metabolic syndrome, and cardiovascular and renal diseases. Most patients with these metabolic diseases exhibit reduced serum FGF19 levels, which might contribute to its etiology.

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	248.6	3.4	1.4
2	8	63.3	1.6	2.5
3	8	31.0	0.9	3.1

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	16	248.9	3.8	1.5
2	16	63.2	1.6	2.5
3	16	31.3	0.9	2.9

RECOVERY

The recovery of human FGF19 spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average% of Expected	Range (%)
Human plasma	1:16	92	91-93
Cell culture supernatant	1:160	82	75-87

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 was initially diluted 1:40.)

		Human plasma	Cell culture supernatant
1:2	Average% of Expected	100	100
	Range (%)	-	-
1:4	Average% of Expected	108	96
	Range (%)	106-110	88-104
1:8	Average% of Expected	118	98
	Range (%)	116-120	87-109
1:16	Average% of Expected	109	92
	Range (%)	100-119	90-94

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human FGF19 produced at Sunlong Medical™.