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The protein concentration of blood coagulation factor VII can be measured equally well in plasma and serum
E M Bladbjerg1, K Overgaard, J Gram
1Institute for Thrombosis Research, South Jutland University Centre, Esbjerg, Denmark.
Insights
Factor VII (FVII:Ag) protein concentration can be reliably measured in both plasma and serum samples. This finding supports using serum for FVII:Ag testing, a potential risk marker for ischemic heart disease.
Area of Science:
- Biochemistry
- Cardiovascular Medicine
- Clinical Chemistry
Background:
- Factor VII coagulant activity (FVII:C) is a known risk marker for ischemic heart disease.
- Factor VII antigen (FVII:Ag) in a fasting state may be a superior risk marker due to assay precision.
- Current FVII:Ag analyses predominantly use plasma, with uncertainty regarding FVII consumption during coagulation.
Purpose of the Study:
- To investigate the comparability of FVII:Ag measurements in plasma versus serum samples.
- To determine if FVII:Ag can be accurately assessed in serum, potentially simplifying sample handling and analysis.
Main Methods:
- Measurement of FVII:Ag in 88 paired plasma and serum samples.
- Statistical comparison of plasma and serum FVII:Ag results using linear regression analysis.
- Assessment of agreement between plasma and serum measurements, including mean differences and standard deviations.
Main Results:
- Linear regression showed a strong correlation (r=0.96) between FVII:Ag in plasma and serum (y = 0.984 x + 0.770).
- No systematic variation was observed between FVII:Ag levels in plasma and serum.
- The mean difference between plasma and serum FVII:Ag was -1.17 (SD 11.92) arbitrary units, comparable to assay variability.
Conclusions:
- There is good agreement between Factor VII antigen (FVII:Ag) measurements in plasma and serum.
- Serum samples are suitable for FVII:Ag analysis, offering a viable alternative to plasma.
- This supports the potential use of serum for FVII:Ag risk assessment in ischemic heart disease.
Abstract:
In the Northwick Park Heart Study, the coagulant activity of factor VII (FVII:C) has been identified as a risk marker of ischaemic heart disease. In the fasting state, the protein concentration of FVII (FVII:Ag) might be an even better risk marker, because of the low coefficient of variation of the antigen assay. Today, most analyses are performed in plasma samples, as it is unknown whether FVII, to some extent, is consumed during coagulation. In the present study, we have investigated, whether FVII:Ag can be measured equally well in plasma and serum. FVII:Ag was measured in 88 plasma and serum samples. Results were compared by means of linear regression, where y = 0.984 x +0.770, r = 0.96. No systematic variation existed between FVII:Ag in plasma and serum. The mean difference in FVII:Ag between plasma and serum was -1.17 (SD 11.92) arbitrary units, compared with a mean difference of 0.18 (SD 8.31) arbitrary units between duplicate measurements of the same plasma dilution. Our findings indicate that there is a good agreement between FVII:Ag in plasma and serum.