Accuracy of Capillary Blood for the Determination of Packed Cell Volume and Anemia among Pregnant Women in Enugu, Nigeria

Abstract

Background: Venous blood packed cell volume (PCV) in pregnancy differs from capillary blood PCV. How this disparity affects the accuracy of capillary blood in determining the actual (venous) PCV is not clear.

Objectives: To determine the accuracy of capillary blood for the determination of actual PCV and anemia among pregnant women in Enugu, Nigeria.

Methods: Pairs of venous and capillary blood of 200 consecutive pregnant women were assessed for PCV, at the antenatal clinic of UNTH, Enugu, Nigeria, from May to June 2012. Using venous blood as the gold standard, standard measures were used to assess the accuracy of capillary PCV (cPCV).

Results: Capillary PCV (median = 34.0%, IQR = 31.0-35.8) of participants differed significantly from their venous PCV (median = 34.0%, IQR = 32.0-37.0), P < 0.001. Mean percentage error for cPCV was -2.3 ± 4.44%. The sensitivity and specificity of cPCV for the determination of anemia were 93.0% and 89.5% respectively. Area under the curve (AUC) of the ROC curve showed an overall high accuracy of cPCV for determination of anemia in pregnancy (AUC = 0.963, p < 0.001).

Conclusions: cPCV showed fairly high accuracy for the determination of anemia in pregnancy in Enugu, Nigeria. However, it systematically underestimates the actual PCV in the study population which suggests that it is inferior to vPCV and may have clinical implication as regards the decision to transfuse. Maternity units should use vPCV when moderate or severe anemia are suspected.