The Quantikine Human CXCL4/PF4 Immunoassay is a 4.5 hour solid-phase ELISA designed to measure human PF4 in cell culture supernates, serum, and platelet-poor plasma. It contains E. coli-expressed recombinant human PF4 and has been shown to accurately quantitate the recombinant factor. Results obtained using natural human PF4 showed linear curves that were parallel to the standard curves obtained using the Quantikine kit standards. These results indicate that this kit can be used to determine relative mass values for naturally occurring human PF4. Range: 0.78 - 50 ng/mL. Sensitivity: 0.1 ng/mL. Time: 4.5 hours