Indirect solid phase enzyme immunoassay (ELISA) for the qualitative screening of IgG class autoantibodies against extractable nuclear antigens (ENA) in human serum or plasma. The assay is intended for in vitro diagnostic use only as an aid in the diagnosis of rheumatic diseases such as systemic lupus erythematosus (SLE), Sjögren´s syndrome, scleroderma and mixed connective tissue disease.
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Catalog Number TK01270
Species Human
Design Indirect solid phase enzyme immunometric assay (ELISA) technique.
Standards 1 cut-off control, ready to use.
Controls 1 negative and 1 positive control, ready to use.
Sample Types Human serum or plasma.
Sample Volume 100 μL of properly diluted (1:100) unknown / determination.
Assay Desc. 30 min. incubation (RT) + 15 min. (RT) + 15 min. (RT) + 5 min. (RT) = 1 hour, 5 min. total incubation time.
Standard Range Calculated cut-off value used to interpret results of unknowns.
Other Names
Storage 2 - 8°C
Postscript For research use only, not for use in diagnostic procedures.

Intended use

This ELISA kit applies to the in vitro quantitative determination of ENA Screen concentrations in serum, plasma and other biological fluids.

Test principle

This ELISA kit uses the Sandwich-ELISA principle. The micro ELISA plate provided in this kit has been pre-coated with an antigen specific to ENA Screen. Standards or samples are added to the micro ELISA plate wells and combined with the specific antigen. Then a biotinylated detection antigen specific for ENA Screen and Avidin-Horseradish Peroxidase (HRP) conjugate are added successively to each micro plate well and incubated. Free components are washed away. The substrate solution is added to each well. Only those wells that contain ENA Screen, biotinylated detection antigen and Avidin-HRP conjugate will appear blue in color. The enzyme-substrate reaction is terminated by the addition of stop solution and the color turns yellow. The optical density (OD) is measured spectrophotometrically at a wavelength of 450 nm ± 2 nm. The OD value is proportional to the concentration of ENA Screen. You can calculate the concentration of ENA Screen in the samples by comparing the OD of the samples to the standard curve.

Typical data

As the OD values of the standard curve may vary according to the conditions of the actual assay performance (e.g. operator, pipetting technique, washing technique or temperature effects), the operator should establish a standard curve for each test. Typical standard curve and data is provided below for reference only.


Intra-assay Precision (Precision within an assay):
3 samples with low, middle,high concentration of ENA Screen. And the sample of ENA Screen were tested 30 times on one plate, respectively.
Inter-assay Precision (Precision between assays):
3 samples with low, middle,high concentration of ENA Screen. And the sample of ENA Screen were tested on 3 different plates, 30 replicates in each plate.


Matrices listed below were spiked with certain level of ENA Screen and the recovery rates were calculated by comparing the measured value to the expected amount of ENA Screen in samples.

Matrix Recovery range (%) Average Recovery (%)
Serum (n=5) 94-104 98
EDTA plasma (n=5) 87-104 95
heparin plasma (n=5) 82-99 95


The linearity of the kit was assayed by testing samples spiked with appropriate concentration of ENA Screen and their serial dilutions. The results were demonstrated by the percentage of calculated concentration to the expected.

    Serum (n=5) EDTA plasma (n=5) heparin plasma (n=5)
1:2 Range (%) 94-103 87-99 92-102
Average (%) 93 95 94
1:4 Range (%) 89-103 91-103 92-107
Average (%) 95 94 94
1:8 Range (%) 92-103 90-107 89-108
Average (%) 95 94 95
1:16 Range (%) 91-103 90-103 90-108
Average (%) 94 94 94


The stability of ENA Screen is determined by the loss rate of activity. The loss rate of ENA Screen is less than 5% within the expiration date under appropriate storage condition. To minimize extra influence on the performance, operation procedures and lab conditions, especially room temperature, air humidity, incubator temperature should be strictly controlled. It is also strongly suggested that the whole assay is performed by the same operator from the beginning to the end.

Item Specifications Storage
Micro ELISA Plate(Dismountable) 8 wells ×12 strips -20℃, 6 months
Reference Standard 2 vials
Concentrated Biotinylated Detection Ab (100×) 1 vial, 120 μL
Concentrated HRP Conjugate (100×) 1 vial, 120 μL -20℃(shading light), 6 months
Reference Standard & Sample Diluent 1 vial, 20 mL 4℃, 6 months
Biotinylated Detection Ab Diluent 1 vial, 14 mL
HRP Conjugate Diluent 1 vial, 14 mL
Concentrated Wash Buffer (25×) 1 vial, 30 mL
Substrate Reagent 1 vial, 10 mL 4℃(shading light)
Stop Solution 1 vial, 10 mL 4℃
Plate Sealer 5 pieces
Product Description 1 copy
Certificate of Analysis 1 copy

Other supplies required

Microplate reader with 450 nm wavelength filter
High-precision transfer pipette, EP tubes and disposable pipette tips
Incubator capable of maintaining 37℃
Deionized or distilled water
Absorbent paper
Loading slot for Wash Buffer

Assay procedure summary

1. Prepare all reagents, samples and standards;
2. Add 100µL standard or sample to each well. Incubate 1 hours at 37°C;
3. Aspirate and add 100µL prepared Detection Reagent A. Incubate 1 hour at 37°C;
4. Aspirate and wash 3 times;
5. Add 100µL prepared Detection Reagent B. Incubate 30 minutes at 37°C;
6. Aspirate and wash 5 times;
7. Add 90µL Substrate Solution. Incubate 10-20 minutes at 37°C;
8. Add 50µL Stop Solution. Read at 450nm immediately.

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