Used in cancer research and clinical studies to detect and quantify CYFRA 21-1, a soluble fragment of cytokeratin 19, in human serum or plasma. Elevated levels are associated with epithelial cell damage and are commonly observed in non-small cell lung cancer, particularly squamous cell carcinoma. The kit supports early detection, monitoring of treatment response, and follow-up of disease recurrence. It is also applied in studies involving other carcinomas such as bladder, cervical, and breast cancer where cytokeratin expression is altered. The ELISA format allows for high sensitivity and specificity in research settings.