Description:
<jats:title>Abstract</jats:title>
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<jats:bold>Background:</jats:bold> The Marburg I (MRI) single nucleotide polymorphism (SNP) of the factor VII-activating protease (<jats:italic>FSAP</jats:italic>) gene has been associated with thrombophilia and atherosclerotic disease. PCR is used to detect the SNP. Also, the specific FSAP activity to cleave single-chain urokinase-type plasminogen activator (scu-PA) serves as a surrogate for PCR testing. Development of further assays is indicated in order to increase testing opportunities for future studies.</jats:p>
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<jats:bold>Methods:</jats:bold> A direct chromogenic substrate immuno-capture activity assay for FSAP (FSAP dcs activity assay) was established. Performance characteristics of the FSAP dcs activity assay were compared to the FSAP scu-PA activity assay.</jats:p>
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<jats:bold>Results:</jats:bold> The FSAP dcs activity assay detects FSAP activity from 25% to 150% of the norm. Total CVs ranged from 6% to 10% for FSAP wild type samples and 9%–18% for MRI samples. Correlation between the FSAP dcs and scu-PA activity assays was low (R=0.7). The FSAP dcs activity determined the presence of the MRI FSAP alloenzyme with a diagnostic sensitivity and specificity of 100% [95% confidence interval (CI): 89.6%–100%] and 96.2% (95% CI: 93.2%–97.4%), respectively, whereas the specific FSAP dcs activity increased specificity to 99.0% (95% CI: 97.2%–99.6%).</jats:p>
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<jats:bold>Conclusions:</jats:bold> The specific FSAP dcs activity represents a reliable method for the detection of the FSAP MRI alloenzyme. Due to the limited correlation between the FSAP dcs and scu-PA activity assays, these different measurands may exhibit different utility in research and clinical applications. Thus, the FSAP dcs activity assay can represent a valuable complement or alternative for FSAP testing in future studies.</jats:p>