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https://www.sekbio.com/products/cytokeratin-19-fragment-cyfra21-1-tumor-marker/ ↗

Cytokeratins are epithelial markers whose expression don't lose during malignant transformation.
CYFRA 21–1 is a cytokeratin 19 fragment soluble in serum and can use as a circulating tumour marker. Although expressed in all body tissues, it is significant in the lung, particularly lung cancer tissues.
CYFRA 21–1 is a sensitive and specific tumour marker of non-small-cell lung cancer (NSCLC), especially the squamous cell subtype.
It also reflects the extent of the disease and has an independent prognostic role along with performance status and disease stage in NSCLC.
In addition, detection of serum CYFRA 21 1 allows for identifying high-risk patients that may benefit from adjuvant chemotherapy and enables the early detection of progressive disease in recurrent NSCLC.
Additionally, CYFRA 21–1 describe as a valuable marker for oesophagal squamous cell carcinoma and therapy monitoring of bladder cancer.

The performance data of the CYFRA21-1 Rapid Quantitative Test Kit (CLIA)
Manufacturer SEKBIO
Parameter CYFRA21-1
Linearity 0.1-500 ng/ml
Detection limit 0.1 ng/ml
benchmark product Roche
Test principle and procedure CYFRA21-1: Add 10 μl of sample + 30 μl of Ra, incubation for 10 minutes cleaning, 30 μl of Rd incubation for 5 minutes. Wash with 200 μl of washing solution. Finally, add 100 μl of A + 100 μl of B.

Six point calibration test results
Sample Concentration( ng/ml)
RLU Average CV S/N
546.75 4,445,546 4,404,255 4,487,587 4,445,796 0.94% 4231.40
93.62 706,516 710,963 736,349 717,943 2.24% 683.32
9.57 69,190 68,756 68,034 68,660 0.85% 65.35
1.03 7,703 7,728 7,799 7,743 0.64% 7.37
0.11 1,703 1,727 1,553 1,661 5.68% 1.58
0.01 1,181 1,003 968 1,051 10.87% 1.00 

Precision
Sample RLU Concentration Sample RLU Concentration





1 6,482 0.76




75 552,944 72.72
5,679 0.72 564,704 74.21
6,317 0.80 563,241 74.03
5,976 0.77 558,522 73.43
6,211 0.82 570,900 75.00
5,873 0.81 566,827 74.48
6,055 0.79 545,138 71.72
6,028 0.79 573,240 75.30
5,927 0.82 550,118 72.36
6,166 0.84 555,993 73.10
AVE 6,71.40 0.79 AVE 560,162.70 73.63
SD 231.61 0.03 SD 9187.21 1.17
CV 3.8% 4.3% CV 1.6% 1.6%

Limit of detection
Sample RLU Concentration




Ag Diluent 1,108 1,164 0.025 0.016
1,124 1,128 0.019 0.019
1,024 1,037 0.003 0.001
1,103 1,103 0.015 0.015
1,055 1,090 0.013 0.007
1,118 1,043 0.004 0.018
1,094 1,183 0.029 0.013
1,040 1,082 0.011 0.004
947 918 0 0
1,054 1,110 0.016 0.006
AVE 1,076.25 0.01
SD 64.60 0.01
AVE+2*SD 0.028

Linear
Sample（ng/ml) Dilution ratio Concentration value Average
438.24 1.0 448.87 443.83 422.03 438.24
350.61 0.8 337.81 349.19 342.22 343.07
262.98 0.6 243.27 247.31 232.15 240.91
175.35 0.4 148.61 151.02 151.09 150.24
87.72 0.2 72.49 69.26 69.64 70.46
0.09 0.0 0.08 0.10 0.09 0.09 
Method Comparison
Reagents Stability
Reagent Sample(ng/ml) Average Deviation
2-8℃ 70.00 2,862,814
10.00 424,472
0.10 9,674
Antigen diluent 4,025
random sample 21,808
calf serum 4,816
37℃ 1d 70.00 2,717,873 -5.06%
10.00 415,759 -2.05%
0.10 9,322 -3.64%
Antigen diluent 4,062 0.91%
random sample 21,842 0.16%
calf serum 4,626 -3.96%
37℃ 3d 70.00 2,720,985 -4.95%
10.00 434,677 2.40%
0.10 9,822 1.52%
Antigen diluent 4,339 7.80%
random sample 22,399 2.71%
calf serum 4,965 3.09%
37℃ 7d 70.00 2,683,682 -6.26%
10.00 408,162 -3.84%
0.10 9,285 -4.02%
Antigen diluent 4,224 4.93%
random sample 23,879 9.49%
calf serum 5,120 6.31%

Cytokeratin 19 Fragment (CYFRA21-1) Products
Name Application
Mouse anti-human CYFRA21-1 mAb For immunodiagnostic: ELISA, LFA, CLIA
Humanized anti-human CYFRA21-1 mAb

CYFRA21-1 Intro
In malignant epithelial cells, the activated protease accelerates the degradation of the cells so that a large number of cytokeratin fragments are released into the blood, and the soluble pieces can specifically bind to the two monoclonal antibodies KS19.1 and BM19.21, so it is called CYFRA21 -1. In malignant lung cancer tissues, CYFRA21-1 is abundant, especially in lung squamous cell carcinoma. The molecular weight of CYFRA21-1 is about 30,000 Da.

The serum level of CYFRA21-1 was not related to age, gender, smoking, and pregnancy. Pneumonia, tuberculosis, bronchitis, bronchial asthma, emphysema, and other diseases generally do not cause CYFRA21-1 elevation. Benign liver disease renal failure can cause a slight increase, but rarely more than 10ng/ml.

Cytokeratin Tumor Marker
Cytokeratin (CK) classifies intermediate filaments that constitute the cytoskeleton. There are many types, among which the cytokeratin 19 (CK19) fragment CYFRA21-1 is the most important in the diagnosis of malignant tumors; the release of CK19 increases when cells become cancerous. , After CK19 is degraded by protease or apoptosis, its fragments are released into the blood. The expression of different keratin fragments has the specificity of tissue distribution, squamous cell carcinoma and adenocarcinoma mainly express CK19, small cell undifferentiated carcinoma mainly express CK18 or only a tiny amount of CK19. CYFRA21-1 is a fragment of cytokeratin 19. It is composed of two monoclonal antibodies to cytokeratin 19, the main component of the cell structure. It is mainly found in the cytoplasm of tumor cells of epithelial origin, such as lung cancer and esophageal cancer. All lung squamous cell carcinomas express CYFRA21-1. When the cells become cancerous, the release of CYFRA21-1 due to the necrolysis of tumor cells increases the blood content, reflecting the prognosis and therapeutic efficacy of the disease. Since the serum product of CK19, CYFRA21-1, is a non-organ-specific tumor marker, comprehensive analysis of clinical data should be combined in clinical application to make a more accurate judgment.

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