Heparin assay.

(a) Identification. A heparin assay is a device used to determine the level of the anticoagulant heparin in the patient's circulation. These assays are quantitative clotting time procedures using the effect of heparin on activated coagulation factor X (Stuart factor) or procedures based on the neutralization of heparin by protamine sulfate (a protein that neutralizes heparin). (b) Classification. Class II (performance standards). [45 FR 60623, Sept. 12, 1980]