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High A1c in Some Subjects May Not Indicate Prediabetes

A new study has shown that for people with iron-deficiency anemia, elevated A1c’s may not reflect glycemic parameter.

"The use of HbA1c to diagnose prediabetes and diabetes in iron-deficient populations may lead to a spuriously exaggerated prevalence," the researchers cautioned in their published report.

Dr. Chittaranjan S. Yajnik of King Edward Memorial Hospital Research Center in Pune, India, wrote that, "A1c concentration depends not only on prevailing glycemia but also the life span of erythrocytes."

"Iron deficiency increases erythrocyte survival and therefore disproportionately elevates HbA1c concentrations at a given glycemic level," they note.

It the current study, the team studied 116 young adults enrolled in a longitudinal cohort study. Among this group, 34% were anemic, 37% were iron deficient, 40% were vitamin B12 deficient, and 22% were folate deficient, the authors note.

Prediabetes was prevalent in 7.8% and diabetes in 2.6%, based on a standard oral glucose tolerance test (OGTT), while corresponding rates based on American Diabetes Association HbA1c criteria were 23.3% for prediabetes and 2.6% for diabetes, the researchers found.

"A total of 24 participants who were normoglycemic by OGTT criteria were misclassified as having prediabetes or diabetes by HbA1c criteria, and six prediabetic or diabetic participants were misclassified as normal by HbA1c criteria," they report.

On further analysis, HbA1c was predicted not only by higher glycemia but also by lower ferritin, the report indicates.

"Our results support a substantial nonglycemic nutritional influence on HbA1c concentrations in young nondiabetic Indians," Dr. Yajnik and colleagues conclude. "This complicates the use of HbA1c in the diagnosis of prediabetes in nutritionally compromised populations (i.e., more than half of the world’s population)."

Diabetes Care Online Feb 8 2012