Description
Introduction: Cytokeratins are intermediate filament structural proteins found in the cytoskeleton of epithelial tissue. They are divided into two types based on sequence homology: acidic type I cytokeratins and basic or neutral type II cytokeratins. Cytokeratins are usually found as dimers composed of a type I and a type II cytokeratin, which are further organized into filamentous structures by forming tetramers. Elevated serum concentrations of specific cytokeratins are observed in patients with lung cancer of all histologic types. A fragment of cytokeratin 19, cytokeratin fragment 21-1 (CYFRA 21-1), has been extensively studied in patients with non-small cell lung cancer and has been demonstrated to be clinically useful. Among tumor marker tests for non-small cell lung cancer, CYFRA 21-1 has consistently been shown to have the highest diagnostic sensitivity (~70 percent). Serum concentrations of CYFRA 21-1 correlate with tumor burden. CYFRA 21-1 is the most sensitive serum tumor marker for non-small cell lung cancer. CYFRA 21-1 is an independent prognostic factor for non-small cell lung cancer. Decreasing concentrations of CYFRA 21-1 after chemotherapy appear to be a reliable marker of treatment efficacy.
Principle of the Assay: The microtiter plate provided in this kit has been pre-coated with an antibody specific to CYFRA21-1. Standards or samples are then added to the appropriate microtiter plate wells with a biotin-conjugated antibody preparation specific for CYFRA21-1 and Avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well and incubated. Then a TMB (3,3',5,5' tetramethyl-benzidine) substrate solution is added to each well. Only those wells that contain CYFRA21-1, biotin-conjugated antibody and enzyme-conjugated Avidin will exhibit a change in color. The enzyme-substrate reaction is terminated by the addition of a sulphuric acid solution and the color change is measured spectrophotometrically at a wavelength of 450 nm +/- 2 nm. The concentration of CYFRA21-1 in the samples is then determined by comparing the O.D. of the samples to the standard curve