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Ferritin concentrations in plasma from capillary (finger prick) blood and venous blood compared
Insights
Finger prick blood tests for plasma ferritin concentration are feasible but overestimate levels compared to venous blood. This overestimation is more pronounced in children, impacting diagnostic accuracy.
Area of Science:
- Clinical Chemistry
- Hematology
- Pediatrics
Background:
- Plasma ferritin concentration is a key indicator of iron status.
- Venous blood sampling is the standard method for ferritin determination.
- Minimally invasive methods for ferritin testing are desirable.
Purpose of the Study:
- To assess the feasibility and validity of measuring plasma ferritin concentration using finger-prick (capillary) blood.
- To compare ferritin levels obtained from capillary blood with those from venous blood.
Main Methods:
- Simultaneous blood collection from antecubital vein and finger prick in 29 adults and 35 children.
- Plasma separation via centrifugation.
- Ferritin concentration measured using immunoradiometric analysis.
Main Results:
- Capillary blood ferritin levels were significantly higher than venous blood levels (p < 0.01).
- The difference was more pronounced in pediatric subjects.
- High correlation (r² = 0.945 adults, 0.994 children) but regression slopes significantly differed from 1 (p < 0.0001).
Conclusions:
- Finger-prick plasma ferritin measurements overestimate venous plasma ferritin concentrations.
- While correlated, capillary blood ferritin results require careful interpretation, especially in children.
Abstract:
Investigating the feasibility and validity of determining plasma ferritin concentration in blood obtained by finger prick, we studied 29 adults (ages 21-49 years) and 35 children (ages 14-66 months). Blood was sampled simultaneously in the same subject from both the antecubital vein (venous blood) and by finger pricking (capillary blood). The plasma was obtained by centrifugation. Ferritin concentration was determined by immunoradiometric analysis. Ferritin concentration in plasma from capillary blood was significantly higher than in venous plasma (p less than 0.01). This difference was more marked in children. The correlation between ferritin from the two blood sources was highly significant (r2 = 0.945 and 0.994 for samples from adults and children, respectively), and the slopes of the respective regression lines in both children and adults were significantly different from 1 (p less than 0.0001). We conclude that, despite the close association between the two procedures, the determination of ferritin concentration in capillary blood plasma overestimates the concentration of ferritin in venous blood plasma.