TISSUE FACTOR INTERACTIONS WITH FACTOR-VII - MEASUREMENT AND CLINICAL-SIGNIFICANCE OF FACTOR VIIA IN PLASMA

Certain epidemiological studies have implicated elevated factor VII co agulant activity as a risk factor for ischaemic heart disease. However , progress in understanding the clinical significance of elevated plas ma factor VII levels has been hampered by: (1) differences between lab oratories in the methodology for measuring factor VII; (2) the existen ce of multiple forms of factor VII in plasma (i.e. factor VIIa, zymoge n factor VII, and a possible phospholipase-sensitive form of factor MI ); (3) the resulting uncertainty regarding what is actually being meas ured in factor VII coagulant assays. Recent mutagenesis studies of tis sue factor (the obligate protein cofactor for factor VIIa) have led to new assay technologies capable of quantifying trace levels of plasma factor VIIa without interference from zymogen factor VII. This review article focuses on the current status of measurement of plasma factor VII/VIIa levels and the relationship between various plasma forms of f actor VII and risk of thrombotic disease.