In the JournalsPerspective

Single blood sample accurately diagnoses diabetes

A single blood sample indicating elevated fasting glucose and HbA1c levels is strongly predictive of a diabetes diagnosis, according to a study published in Annals of Internal Medicine.

“Current clinical definitions of diabetes require repeated blood work to confirm elevated levels of glucose or HbA1c to reduce the possibility of a false-positive diagnosis,” Elizabeth Selvin, PhD, MPH, from Johns Hopkins Bloomberg School of Public Health, and colleagues wrote. “Whether two different tests from a single blood sample provide adequate confirmation is uncertain.”

Selvin and colleagues conducted a study to investigate the diagnostic performance of a single blood sample for unconfirmed diabetes. The researchers enrolled 12,268 patients without diagnosed diabetes. Participants were followed for incident diabetes, cardiovascular outcomes, kidney disease and mortality over 25 years.

The researchers defined high levels of fasting glucose (7 mmol/L) and HbA1c (6.5%) from a single blood sample as confirmed undiagnosed diabetes. Unconfirmed undiagnosed diabetes was defined as having only one elevated measure.

A single blood sample indicating elevated fasting glucose and HbA1c levels is strongly predictive of a diabetes diagnosis.
Photo credit: Adobe Stock

At baseline, elevated levels of fasting glucose or HbA1c were documented in 978 participants. Confirmed undiagnosed diabetes was seen in 39% of these participants, whereas unconfirmed undiagnosed diabetes was seen in 61%.

During follow-up, the confirmatory definition of undiagnosed diabetes had moderate sensitivity (54.9% at 5 years) and high specificity for identifying diagnosed diabetes cases (98.1% at 5 years and 99.6% at 15 years). After 15 years, the positive predictive value of the single sample was 88.7% for confirmed undiagnosed diabetes and 71.1% for unconfirmed.

Participants with confirmed undiagnosed diabetes were significantly likely to experience CVD, kidney disease, peripheral artery disease and mortality.

“Our findings support clinical use of a combination of HbA1c and fasting glucose levels from a single blood sample to identify cases of undiagnosed diabetes in the population, although these results will need to be confirmed in other data sets,” Selvin and colleagues concluded.

They noted that the new diagnostic method would eliminate the need for a second blood test.

In an accompanying editorial, K.M. Venkat Narayan, MD, MSc, MBA, and Ram Jagannathan, PhD, both from Emory University, noted that detecting diabetes early and simplifying approaches to do so is imperative to prevent or delay complications. The findings by Selvin and colleagues offer a promising new way to improve the timing and efficiency of diabetes diagnosis, they wrote.

“Selvin and colleagues offer an innovative and practical use of a single blood sample at one visit, rather than two samples obtained at two visits, to confirm the diagnosis of diabetes,” they wrote. “This approach has appeal, especially for resource-challenged settings, but it needs replication in other populations before becoming accepted clinical practice.” – by Alaina Tedesco

Disclosure: Jagannathan, Selvin and Venkat Narayan report no relevant financial disclosures. Please see study for all other authors’ relevant financial disclosures.

A single blood sample indicating elevated fasting glucose and HbA1c levels is strongly predictive of a diabetes diagnosis, according to a study published in Annals of Internal Medicine.

“Current clinical definitions of diabetes require repeated blood work to confirm elevated levels of glucose or HbA1c to reduce the possibility of a false-positive diagnosis,” Elizabeth Selvin, PhD, MPH, from Johns Hopkins Bloomberg School of Public Health, and colleagues wrote. “Whether two different tests from a single blood sample provide adequate confirmation is uncertain.”

Selvin and colleagues conducted a study to investigate the diagnostic performance of a single blood sample for unconfirmed diabetes. The researchers enrolled 12,268 patients without diagnosed diabetes. Participants were followed for incident diabetes, cardiovascular outcomes, kidney disease and mortality over 25 years.

The researchers defined high levels of fasting glucose (7 mmol/L) and HbA1c (6.5%) from a single blood sample as confirmed undiagnosed diabetes. Unconfirmed undiagnosed diabetes was defined as having only one elevated measure.

A single blood sample indicating elevated fasting glucose and HbA1c levels is strongly predictive of a diabetes diagnosis.
Photo credit: Adobe Stock

At baseline, elevated levels of fasting glucose or HbA1c were documented in 978 participants. Confirmed undiagnosed diabetes was seen in 39% of these participants, whereas unconfirmed undiagnosed diabetes was seen in 61%.

During follow-up, the confirmatory definition of undiagnosed diabetes had moderate sensitivity (54.9% at 5 years) and high specificity for identifying diagnosed diabetes cases (98.1% at 5 years and 99.6% at 15 years). After 15 years, the positive predictive value of the single sample was 88.7% for confirmed undiagnosed diabetes and 71.1% for unconfirmed.

Participants with confirmed undiagnosed diabetes were significantly likely to experience CVD, kidney disease, peripheral artery disease and mortality.

“Our findings support clinical use of a combination of HbA1c and fasting glucose levels from a single blood sample to identify cases of undiagnosed diabetes in the population, although these results will need to be confirmed in other data sets,” Selvin and colleagues concluded.

They noted that the new diagnostic method would eliminate the need for a second blood test.

In an accompanying editorial, K.M. Venkat Narayan, MD, MSc, MBA, and Ram Jagannathan, PhD, both from Emory University, noted that detecting diabetes early and simplifying approaches to do so is imperative to prevent or delay complications. The findings by Selvin and colleagues offer a promising new way to improve the timing and efficiency of diabetes diagnosis, they wrote.

“Selvin and colleagues offer an innovative and practical use of a single blood sample at one visit, rather than two samples obtained at two visits, to confirm the diagnosis of diabetes,” they wrote. “This approach has appeal, especially for resource-challenged settings, but it needs replication in other populations before becoming accepted clinical practice.” – by Alaina Tedesco

Disclosure: Jagannathan, Selvin and Venkat Narayan report no relevant financial disclosures. Please see study for all other authors’ relevant financial disclosures.

    Perspective
    Om P. Ganda

    Om P. Ganda

    Type 2 diabetes is a slowly progressive disease. Prediabetes may progress to diabetes without any symptoms at the rate of 10-15% per year depending on age, ethnic, and other factors, although some may never progress to diabetes. Diagnosing diabetes early is very important to prevent long-term complications.

    Currently, there are three established criteria for diagnosing undiagnosed diabetes. These include a fasting blood glucose ≥ 126 mg/dL, a glucose level ≥200 mg/dL, 2 hours after 75 gm glucose, and an HbA1C ≥ 6.5%. There is a considerable discordance between these tests and checking all three will most frequently correctly diagnose diabetes.

    However, the 2-hour glucose level requires a longer visit and is inconvenient. Therefore, most often, a single fasting sample is obtained for both fasting blood glucose and HbA1C measurements. However, the American Diabetes Association and most others recommend re-checking those numbers once more another day, for a more accurate diagnosis.

    In this study, Selvin et al investigated if a single sample for fasting blood glucose and HbA1C in people with undiagnosed diabetes will diagnose more people with confirmed undiagnosed diabetes on long-term follow-up, depending on whether one or both tests were positive at baseline.

    Indeed, they were able to show that those with both tests positive at baseline could be four to five times more likely to be diagnosed with diabetes than those with only one test positive. In addition, those with confirmed undiagnosed diabetes were more likely to develop cardiovascular and kidney complications.

    One noteworthy limitation was that about 80% of the subjects in this study were white, and Asians and Hispanics were not included. The results may be different in them.

    • Om P. Ganda, MD
    • Senior Physician and Director, Lipid Clinic Chair, Clinical Oversight Committee Joslin Diabetes Center Associate Professor of Medicine, Harvard Medical School

    Disclosures: Ganda reports no relevant financial disclosures.