Validation of hemoglobin estimation using Hemocue

This piece of work is an attempt to compare Hemocue and Cyanmethemoglobin methods for hemoglobin estimation.

In 100 apparently healthy children of 1-6 years of age, Hb was estimated using Hemocue and cyanmethemoglobin methods from finger prick blood sample. The results obtained by the two methods were compared using appropriate statistical methods.

Mean +/- SD values for hemoglobin (g/dl) were 9.33 +/- 2.719 by Hemocue and 8.14 +/- 2.448 by cyanmethemoglobin method. When assessed by Hemocue method the proportion of children with anemia was 66% while it was 88% with cyanmethemoglobin method. The sensitivity of Hemocue method was 0.75 and specificity 1.0 considering cyanmethemoglobin method as gold standard. The corresponding values by cyanmethemoglobin method for a given Hemocue value fell within the Mean difference +/- 2 SD with correlation coefficient being r = 0.922. Despite the good association, the two methods agreed, the magnitude of difference being -1.19 g/dl (CI: -1.40 to -0.98) thus suggesting an overestimate of hemocue values ranging from 10 to 15%. A correction factor was arrived for converting Hb values obtained by Hemocue method to arrive at the expected value by the reference method, this factor being 0.389 + 0.831 Hb (Hemocue).

As there are limitations expressed for both the methods in accurately estimating Hb, it is difficult to decide whether one is an overestimate or the other an underestimate. By virtue of the principle involved in estimating Hb, cyanmethemoglobin method may be taken as an indirect indicator of iron status. However, it is not clear whether such a principle is involved in estimating Hb by Hemocue. Therefore, these two methods need to be further validated against a sensitive and specific indicator for iron status like circulating transferrin receptor to decide which of the methods can be used to accurately determine the prevalence of iron deficiency anemia in the community.