Comparison of venipuncture blood counts with microcapillary measurements in screening for anemia in one-year-old infants

Abstract

The microhematocrit measurement of fingerstick blood in infants gives elevated values compared to venous hematocrits measured simultaneously in a Coulter Model S electronic counter. Thirty one-year-old infants had a mean microhematocrit of 36.6, significantly higher (p less than 0.001) than the mean venous Coulter S hematocrit of 34.6. Three children, who appeared to be normal by microhematocrit measurement, were found to be anemic by Coulter S measurement; in these children the microhematocrits were elevated 13.6%, 12.5%, and 5.1%, respectively, above venous Coulter S levels. Complete blood counts were measured concurrently on venipuncture specimens and on capillary samples. There was excellent correlation for mean cell volume (r = 0.98), but poor correlation for hemoglobin (r = 0.81) and hematocrit (r = 0.77). Four of 30 children had borderline low venipuncture hemoglobin values (less than or equal to 11.5 gm/dl) that were not detected by the capillary method. The inaccuracy of the fingerstick microhematocrit method and the discrepancy between the venipuncture and capillary Coulter S values supports the choice of venipuncture blood counts as the preferred method of screening for anemia in one-year-old infants.