SEM of red blood corpuscles. Credit: David Gregory & Debbie Marshall

Study Group assessing the relationship between haemoglobin and haematocrit measurements

13 March 2019

Haemoglobin-Haematocrit Relationship in Malaria Study Group is assessing the accuracy of estimating haemoglobin (Hb) levels from haematocrit (Hct) levels. The aim is to use this analysis to derive a more robust formula for converting Hct to Hb levels to improve anaemia diagnosis in malaria.

In countries where malaria is endemic, anaemia is a common and a well-known complication of malaria, which can exacerbate symptoms. Young children, pregnant women and people who are malnourished are particularly vulnerable. Severe anaemia is the leading cause of death in children with anaemia.

WWARN’s Head of Statistics, Kasia Stepniewska says, “The Haemoglobin-Haematocrit Relationship in Malaria Study Group aims to assess the accuracy of the two existing methods and determine what pre-defined covariates affect the Hb-Hct relationship. We’re excited to have started this analysis as it could potentially develop a new, more robust method to improve anaemia diagnosis.”

The most accurate way to diagnose anaemia is to measure Hb levels in the blood. This directly estimates the blood’s ability to carry oxygen. Measuring Hct levels is also possible, although this is a more indirect measure. In resource-limited settings, it is more common to measure Hct levels, as the method for Hb measurement is more expensive. It is then necessary to convert the Hct level to Hb level for diagnosis.

There are currently two main methods for calculating Hb from Hct, but there are concerns these methods may not lead to an accurate diagnosis. The first method is to divide the Hct level by 3, but this could mean Hb is overestimated thus causing under-diagnosis of anaemia. Another conversion method known as Lee’s formula has been proposed after a pooled analysis of 3,254 concurrent measurements from 1,810 patients with Plasmodium falciparum malaria. However, there are concerns with this method because the analyses did not define the effects of factors such as age, sex, malnutrition status as well as the time at which measurements were taken.

 A detailed statistical plan will be shared with contributors.

If you'd like to follow the progress of this Study Group, please visit the Hb-Hct Relationship in Malaria Study Group.

Email your questions to Kasia Stepniewska, Head of WWARN Statistics kasia [dot] stepniewska [at] wwarn [dot] org