Vancouver, B.C. – If a patient is admitted to the hospital with a plasma glucose at or above 140 mg/dL, it’s wise to check the hemoglobin A1c level to catch undiagnosed diabetes, according to British and Irish researchers.
“A combination of admission plasma glucose and hemoglobin A1c can be used to diagnose diabetes in acute medicine, provided care is taken when interpreting hemoglobin A1c results, as they can be affected by various medical conditions or certain drugs,” said investigator Dr. Sandip Ghosh, a diabetologist at Queen Elizabeth Hospital in Birmingham, England.
The conclusion comes from a review of 2,061 white inpatients at University Hospital Waterford (Ireland), 412 (20%) of whom were diagnosed with diabetes on admission or displayed symptoms and complications.
An admission plasma glucose level of 140.4 mg/dL correlated with a hemoglobin A1c of 6.5%, the threshold for diabetes diagnosis. If ordering a hemoglobin A1c is delayed until the plasma glucose reaches 200 mg/dL, “we are missing an awful lot of people with diabetes,” Dr. Ghosh said.
The linear correlation between admission plasma glucose and hemoglobin A1c levels wasn’t perfect (r2 = 0.63, P less than 0.001). The approach was highly specific but not very sensitive, possibly because of a hemoglobin A1c level that has been compromised by liver, renal, or other problems, said investigator Susan Manley, Ph.D., a biochemist at the Birmingham hospital.
The Joint British Diabetes Society is planning to release a nationwide guideline for diabetes screening at hospital admission, but the quickest and most cost-effective way to screen for diabetes is uncertain.
Dr. Ghosh and Dr. Manley are both involved with those efforts, and their study is an attempt to solve the problem. They and their colleagues are planning a prospective study of hemoglobin A1c screening approaches in a more racially diverse population.
Eventually, “we are going to use” these findings to help write the recommendations, but “we need to make sure emergency wards do make the measurements,” and that labs can handle an upsurge in hemoglobin A1c testing, Dr. Manley said.
For now, hemoglobin A1c is generally used to check glucose control in hospital patients already known to have diabetes, both in the United Kingdom and the United States. It’s attractive as a hospital screening tool, however, because it can help discriminate between patients who truly have diabetes and those who are hyperglycemic because of acute illness.
The study analyzed admission plasma glucose, hemoglobin A1c, oral glucose tolerance tests, and other measures in consecutive, short-term medical admissions to the Waterford hospital from 2005 to 2007. The researchers calculated that hemoglobin A1c screening would have identified about 40 more cases of diabetes.
The authors reported no conflicts of interest.