Differences in Composition of Capillary and Venous Blood Specimen
Blood obtained through skin puncture (capillary blood) differs from blood that is obtained through venipuncture. When analyzing the major characteristics of capillary blood, such as pH, PCO2, PO2 and oxygen saturation, freely flowing capillary blood is actually more similar to arterial than to venous blood. On the other hand, due to the method of collection, capillary blood is contaminated with interstitial and intracellular fluids, which will influence the analytic values obtained from these samples. It is for this reason that capillary blood is not recommended for coagulation testing. Differences also exist between venous and capillary blood analyte concentrations (see table below). This is by no means an exhaustive list, and since the data were taken from two different studies, does not include identical analytes for both specimen types, i.e. plasma and serum.
1 From. Kupke 1R, Kather B. Zeugner S. On the composition of Capillary and Venous Blood Serum.
ClIN, CHIM, ACT, 1981; 112; 177-85.
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