CYFRA 21-1 ELISA Kit (Cytokeratin-19 Fragment)


Human CYFRA 21-1 ELISA kit is a procedure designed for detecting in vitro quantitative levels of cytokeratin-19 fragment (CYFRA 21-1) in human serum and plasma (citrate, heparin). This assay has a minimum sensitivity limit of 0.15 ng/ml.


CYFRA 21-1 is a cytokeratin-19 fragment which can be used as a circulating tumor bionarker and it is also soluble in serum. A molecular weight between 25-40 kDa, it is ubiquitously expressed in all connective tissue cells. Even though it is found to be expressed in almost all body tissues, the majority of it occurs in the lung (especially lung cancer tissues). It  is often used in detecting non-small-cell lung cancer (NSCLC), it can accurately reflect the extent of the disease and the disease stage.

The following assay uses two mouse monoclonal antibodies (BM19.21 and KS19.1) in order to determine cytokeratin-19 fragments. The accurate measurement of serum can be used to identify high risk patients who can benefit from adjuvant chemotherapy, this also allow the early detection of progressive disease in recurrent NSCLC. Furthermore, it has been used as a useful marker for esophageal squamous cell carcinoma and during therapy monitoring for bladder cancer.


All reagents supplied need to be stored at 2 °C – 8 °C, unopened reagents will retain reactivity until expiration date. Do not use reagents beyond this date.

  • Microtiterwells: Coated with anti-CYFRA 21-1 antibody (monoclonal).
  • Standard (0-4): Lyophilized, concentrations 0, 3, 10, 25, 50 ng/mL.
  • Control Low & High (Lyophilized).
  • Sample Diluent.
  • Assay Buffer.
  • Enzyme Conjugate: Anti-CYFRA 21-1 antibody conjugated with horseradish peroxidase.
  • Substrate Solution: Tetramethylbenzidine (TMB).
  • Stop Solution: Contains 0.5 M H2SO4.
  • Wash Solution (40x Concentrated).


The minimum detection sensitivity level of cytokeratin-19 fragment (CYFRA21-1, CYFRA-21-1) using current human CYFRA 21-1 ELISA kit was 0.15 ng/ml. The dynamic range for this assay is 3.0 – 50.0 ng/ml.


– Assay Dynamic Range: 0.079 – 50 ng/mL
– Specificity (Cross Reactivity): The antibodies used are specific for keratin 19.
– Sensitivity: The Limit of Blank (LoB) is 0.079 ng/mL. The Limit of Detection (LoD) is 0.185 ng/mL. The Limit of Quantification (LoQ) is 0.343 ng/mL.
– Intra-Assay Variations: 2.7 – 6.4%
– Inter-Assay Variations: 5.5 –11.7%
– Inter Lot Variations: 2.5 –5.2%
– Recovery: 87.7 – 105.5%
– Linearity: 95.5 – 109.1%
– Interfering Substances: Haemoglobin (up to 4 mg/mL), Bilirubin (up to 0.5 mg/mL) and Triglyceride (up to 7.5 mg/mL) have no influence on the assay results.
– Drug Interference: None
– High-Dose-Hook Effect: No hook effect was observed in samples with concentrations higher than 1,000 ng/l of CYRA 21-1.


  1. Different cutoff values of Cyfra 21-1 for cavitary and noncavitary lung cancers. Lung Cancer. (2000) 30 (3): 187-92. Kim Y.C., et al.
  2. Cytokeratin-19 fragment in the diagnosis of bladder carcinoma. Tumour Biol. (2016) 37 (10): 14329-14330. Guo X.G. and Long J.J.
  3. Biomarkers in saliva for the detection of oral squamous cell carcinoma and their potential use for early diagnosis: a systematic review. Acta Odontol Scand. (2016) 74 (3): 170-7. Review. Gualtero D.F. and Suarez Castillo A.
  4. Keratins: Biomarkers and modulators of apoptotic and necrotic cell death in the liver. Hepatology. (2016) 64 (3): 966-76. Review. Ku N.O., et al.


  • Full Name: CYFRA 21-1 ELISA Kit (Cytokeratin-19 Fragment)
  • Reactivity: Human
  • Sample Type: Serum, Plasma (Heparin, Citrate)
  • Sensitivity: 0.15 ng/ml


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