Hemoglobins and hematocrits: are they equally sensitive in detecting anemias?

General medical and nutritional practice assumes that hemoglobin and hematocrit values are equally useful in detecting anemia and that they can be used interchangeably for anemia screening. These two tests, at presumed equivalent levels, identify varying prevalences of anemia in the same population. This study examines anemia prevalence rates using hemoglobin and hematocrit tests performed in seven separate surveys on a total of 13,040 children. These data indicate that hemoglobin and hematocrit screening tests are indeed not comparable in detecting anemia in the same population. Using only hematocrit tests, anemia is diagnosed in 1 to 10% of children with normal hemoglobin levels and is not detected in 20 to 50% of children who might be considered anemic on the basis of low hemoglobin levels.