Human FLRG Quantikine ELISA Kit

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Control Products Available
Human FLRG ELISA Serum/Plasma/Human Milk Standard Curve
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Product Details
Citations (8)
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Human FLRG Quantikine ELISA Kit Summary

Assay Type
Solid Phase Sandwich ELISA
96-well strip plate
Assay Length
4.5 hours
Sample Type & Volume Required Per Well
Cell Culture Supernates (100 uL), Serum (20 uL), EDTA Plasma (20 uL), Heparin Plasma (20 uL), Urine (50 uL), Human Milk (50 uL)
8.55 pg/mL
Assay Range
62.5 - 4,000 pg/mL
Natural and recombinant human FLRG
< 0.5% cross-reactivity observed with available related molecules.< 50% cross-species reactivity observed with species tested.
Interference observed with 1 or more available related molecules.

Product Summary

The Quantikine Human FLRG Immunoassay is a 4.5 hour solid-phase ELISA designed to measure human FLRG in cell culture supernates, serum, plasma, urine, and human milk. It contains NS0-expressed recombinant human FLRG and has been shown to accurately quantitate the recombinant factor. Results obtained using natural human FLRG showed linear curves that were parallel to the standard curves obtained using the Quantikine kit standards. These results indicate that this kit can be used to determine relative mass values for naturally occurring human FLRG.


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

Cell Culture Supernates, Urine

Intra-Assay Precision Inter-Assay Precision
Sample 1 2 3 1 2 3
n 20 20 20 20 20 20
Mean (pg/mL) 468 1113 2252 494 1174 2331
Standard Deviation 10.4 23 55.2 32.9 69 143
CV% 2.2 2.1 2.5 6.7 5.9 6.1

Serum, EDTA Plasma, Heparin Plasma, Human Milk

Intra-Assay Precision Inter-Assay Precision
Sample 1 2 3 1 2 3
n 20 20 20 20 20 20
Mean (pg/mL) 448 1094 2306 486 1148 2282
Standard Deviation 15.4 18.5 49.5 29.5 53 122
CV% 3.4 1.7 2.1 6.1 4.6 5.3


The recovery of FLRG spiked to levels throughout the range of the assay was evaluated.

Sample Type Average % Recovery Range %
Cell Culture Media (n=4) 107 98-111
EDTA Plasma (n=4) 96 85-105
Heparin Plasma (n=4) 102 89-114
Serum (n=4) 100 91-112


To assess the linearity of the assay, samples containing high concentrations of FLRG were serially diluted with the appropriate Calibrator Diluent to produce samples with values within the dynamic range of the assay.
Human Follistatin-related Gene Protein/FLRG ELISA Linearity

Scientific Data

Human FLRG ELISA Serum/Plasma/Human Milk Standard Curve

Human FLRG ELISA Cell Culture Supernate/Urine Standard Curve

Product Datasheets

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Preparation and Storage

The product is shipped at ambient temperature. Upon receipt, store it immediately at the temperature recommended below.
Store the unopened product at 2 - 8 °C. Do not use past expiration date.

Background: Follistatin-related Gene Protein/FLRG

Follistatin-related gene protein (FLRG) has been shown to bind and inhibit the TGF-beta family ligands including activin, BMP-2, -6, -7, and GDF-8. FLRG is expressed most highly in heart, lung, kidney, and placenta, and is upregulated by TGF-beta and Activin via Smad proteins.

Entrez Gene IDs:
10272 (Human); 83554 (Mouse)
Alternate Names:
FLRG; FLRGFSRP; follistatin-like 3 (secreted glycoprotein); Follistatin-like 3; Follistatin-like protein 3; Follistatin-related gene protein; follistatin-related protein 3; FSTL3
⚠ WARNING: This product can expose you to chemicals including N,N-Dimethylforamide, which is known to the State of California to cause cancer. For more information, go to

Assay Procedure

Refer to the product for complete assay procedure.

Bring all reagents and samples to room temperature before use. It is recommended that all samples, standards, and controls be assayed in duplicate.
  1.   Prepare all reagents, standard dilutions, and samples as directed in the product insert.
  2.   Remove excess microplate strips from the plate frame, return them to the foil pouch containing the desiccant pack, and reseal.

  3. 100 µL Assay Diluent
  4.   Add 100 µL of Assay Diluent to each well.

  5. 100 µL Standard, Control, or Sample
  6.   Add 100 µL of Standard, control, or sample to each well. Cover with a plate sealer, and incubate at room temperature for 2 hours on a horizontal orbital microplate shaker.
  7.   Aspirate each well and wash, repeating the process 3 times for a total of 4 washes.

  8. 200 µL Conjugate
  9.   Add 200 µL of Conjugate to each well. Cover with a new plate sealer, and incubate at room temperature for 2 hours on the shaker.
  10.   Aspirate and wash 4 times.

  11. 200 µL Substrate Solution
  12.   Add 200 µL Substrate Solution to each well. Incubate at room temperature for 30 minutes on the benchtop. PROTECT FROM LIGHT.

  13. 50 µL Stop Solution
  14.   Add 50 µL of Stop Solution to each well. Read at 450 nm within 30 minutes. Set wavelength correction to 540 nm or 570 nm.

Citations for Human FLRG Quantikine ELISA Kit

R&D Systems personnel manually curate a database that contains references using R&D Systems products. The data collected includes not only links to publications in PubMed, but also provides information about sample types, species, and experimental conditions.

8 Citations: Showing 1 - 8
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  1. The circulating proteomic signature of alcohol-associated liver disease
    Authors: J Luther, AG Vannier, EA Schaefer, RP Goodman
    JCI Insight, 2022;7(14):.
    Species: Human
    Sample Types: Serum
  2. The Activin/FLRG pathway associates with poor COVID-19 outcomes in hospitalized patients
    Authors: M McAleavy, Q Zhang, PJ Ehmann, J Xu, MF Wipperman, D Ajithdoss, L Pan, M Wakai, R Simonson, A Gadi, A Oyejide, SC Hamon, A Boyapati, LG Morton, T Shavlakadz, CA Kyratsous, DJ Glass
    Molecular and Cellular Biology, 2021;0(0):MCB0046721.
    Species: Human
    Sample Types: Cell Culture Supernates
  3. The RNA landscape of the human placenta in health and disease
    Authors: S Gong, F Gaccioli, J Dopierala, U Sovio, E Cook, PJ Volders, L Martens, PDW Kirk, S Richardson, GCS Smith, DS Charnock-J
    Nature Communications, 2021;12(1):2639.
    Species: Human
    Sample Types: Serum
  4. Serum biomarker for diagnostic evaluation of pulmonary arterial hypertension in systemic sclerosis
    Authors: LM Rice, JC Mantero, EA Stratton, R Warburton, K Roberts, N Hill, RW Simms, R Domsic, HW Farber, R Layfatis
    Arthritis Res. Ther., 2018;20(1):185.
    Species: Human
    Sample Types: Serum
  5. Activin subfamily peptides predict chronological age in humans
    Authors: LV Barrios-Si, M Parnell, ZB Shinwari, GA Chaudhary, T Xenofontos, A van Bekhov, S McArthur, BT Elliott
    Physiol Rep, 2018;6(17):e13823.
    Species: Human
    Sample Types: Plasma
  6. Vitamin D supplementation lowers thrombospondin-1 levels and blood pressure in healthy adults
    Authors: AT Amaraseker, B Assadi-Kha, S Liu, M Black, G Dymmott, NM Rogers, AL Sverdlov, JD Horowitz, DTM Ngo
    PLoS ONE, 2017;12(5):e0174435.
    Species: Human
    Sample Types: Plasma
  7. Serum activin A and follistatin levels in gestational diabetes and the association of the Activin A-Follistatin system with anthropometric parameters in offspring.
    Authors: Naf S, Escote X, Ballesteros M, Yanez R, Simon-Muela I, Gil P, Albaiges G, Vendrell J, Megia A
    PLoS ONE, 2014;9(4):e92175.
    Species: Human
    Sample Types: Serum
  8. Activin subfamily peptides predict chronological age in humans.
    Authors: Barrios-Silva L, Parnell M, Shinwari Z, Chaudhary G, Xenofontos T, van Bekhoven A, McArthur S, Elliott B
    Physiol Rep, 0;6(17):e13823.
    Species: Human
    Sample Types: Plasma


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