Assessing the Validity of the Threefold Conversion between Hemoglobin and Hematocrit for the Determination of Anemia in Pregnancy

Abstract

Introduction: The worldwide prevalence of anemia is higher among pregnant women. Anemic status is determined by the measurement of Hemoglobin (Hb) or Hematocrit (Hct). Hct (%) is usually defined as three times the value of Hb (g/dl). But the crude relationship between the two measures may be modified due to several factors such as; age, sex, season of survey and disease conditions. This study was therefore undertaken with the intent of assessing the validity of the 3- fold conversion between Hb and Hct to assess anemia in pregnant women. Method: The Hb concentrations and Hct values from 70 pregnant mothers, aged 18-30 years, in their first trimester of pregnancy, from the ante-natal clinics of Teaching Hospital, Mahamodara were analyzed. The relationship between the concurrent measures of Hb and Hct was defined by linear regression analysis and the validity of the 3- fold conversion was assessed. Results: The prevalence of anemia as defined by both Hb and Hct levels was 17%. Almost 59% of the microhematocrit values wrongly estimated Hb using 3- fold conversion. Sensitivity and specificity results obtained were below the reliability of clinical measurement. Regression models show that the association between the cut-offs of Hb and Hct is not dependent only on a simple conversion factor and correlation coefficient results are inadequate to conclude that there is a significant relationship between the two variables. A significant difference was observed between the values obtained using the two methods (t= 7.182, p <0.001). Conclusions: The relationship between Hb and Hct is not exactly 3 in pregnant women and there is no simple conversion factor between the two measures. Since the Drabkin's method still has the advantage of being an international standard, this study argues for the consistent use of Hb rather than Hct in the assessment of anemia in pregnancy.