Researchers from India, London and Africa have proposed that the oral glucose tolerance test (OGTT) used to determine if a pregnant woman has developed gestational diabetes be replaced by an HbA1c test that can also be used at the point of care. They have recommended that this be administered in early pregnancy, during the first trimester itself.
In a paper published in The Lancet Diabetes and Endocrinology, authors argued that HbA1c offers a simple screening test for gestational diabetes, allowing those at highest risk to receive early intervention and greatly reduces the need for OGTTs. Researchers used the results from STRiDE, a prospective cohort study, set up in seven centres in south India and seven in western Kenya. Participants were also included from the PRiDE cohort in the U.K..
Testing at home
The proposal is significant for India. More than 90% of gestational diabetes cases are estimated to occur in low-income and middle-income countries. Currently, guidelines recommend that mothers take an OGTT, which is a concentrated 75 g oral solution at fasting, and then wait two to three hours to do a follow up, at the 24 to 28 week stage. This throws up a lot of challenges, particularly in screening women who are in far-flung rural areas and in hard-to-reach areas. In such situations, a trained health care worker can instead be given a point-of-care testing kit and, with just a drop of blood, test the woman for HbA1c at her own home.
The study concluded that in India, a HbA1c result of 4.9 rules out diabetes, while women who have a score of 5.4 or above can be ‘ruled in’ for gestational diabetes. If the risk score classifies them in the lowest risk group, they would not have to take an OGTT; only those in the intermediate group between these two values would have to do the more complicated test. “We roughly estimated this will be around 25% of all pregnant women,” explained P. Saravanan, professor at the Warwick Medical School in the U.K.’s University of Warwick, and one of the authors of the study.
For rural, remote areas
“This would be particularly useful for women living in rural areas and hard-to-reach terrains where OGTT will be impossible to do. Although the direct cost of this is roughly double that of OGTT, if you include the cost of travel, lost wages, etc, it will be cost neutral. Moreover, HbA1c is currently more expensive partly because it is not used routinely. However, more usage will also bring the costs down,” he added.
V. Mohan of the Madras Diabetes Research Foundation, another author of the paper, said the big advantage is that this could help avoid 50% to 64% of all the OGTTs being done currently. “While we believe that the OGTT is a gold standard test and still do it in our labs, using point of care HbA1c test would really make a difference in a public health setting, by being able to reach more women who might otherwise be left out of the net.”
Early intervention
A recent Lancet series on gestational diabetes demonstrated the well-documented fact that it impacts not just the mother, but also the child over the long term. Another of the authors, Uma Ram, who is a senior obstetrician at Chennai’s Seethapathy Clinic, pointed to two advantages to using the HbA1c test: it confers the ability to identify a high-risk group earlier on in pregnancy, and an opportunity to intervene with diet and exercise. There is data that early intervention helps prevent development of gestational diabetes.
Dr. Saravanan added: “Currently, we think only 20% of women get tested by OGTT. We believe we can improve the screening rate significantly with this test. Our next step is to evaluate a HbA1c-based diagnosis vs. OGTT-based diagnosis. I sincerely believe this will slowly relace the OGTT, but further research is necessary.”
