Clinical Laboratory professionals know that point of care test results performed on a fingerstick sample of blood are often less accurate and precise than results performed on a central laboratory analyzer using a venous sample. Improvements in point of care technology have greatly improved the analytical performance of point of care devices. A recent study published in the American Journal of Clinical Pathology convincingly demonstrated that much of the variability in point of care testing occurs during the preanalytical phase of collecting a fingerstick sample of blood.
Compared to tests on venous blood, the coefficient of variation for successive drops of fingerstick blood exceeded venous blood by 3.4 times for hemoglobin, 5.7 times for WBC count, 3.0 times for lymphocyte count, 7.7 times for granulocyte count, and 4.0 times for platelet count. In some individuals, hemoglobin concentration differed by more than two g/dL between two successive drops of blood.
Questionable Accuracy of Point of Care Tests Performed on Fingerstick Blood Samples