Running two tests on single blood sample could provide diabetes diagnosis
In a prospective cohort analysis of patients in the Atherosclerosis Risk in Communities study without diagnosed diabetes at baseline, both fasting glucose and HbA1c level were measured in a single blood sample taken during a visit in 1990 to 1992.
Diabetes may be diagnosed by testing both fasting glucose and HbA1c level with a single blood sample, according to a recent study.
The prospective cohort analysis included 12,268 participants in the Atherosclerosis Risk in Communities study who did not have diagnosed diabetes at baseline. For each participant, both fasting glucose and HbA1c level were measured in a single blood sample taken during a visit in 1990 to 1992. Confirmed undiagnosed diabetes was defined as fasting glucose of 126 mg/dL or higher (≥7.0 mmol/L) and an HbA1c level of 6.5% or above. Participants were followed for 25 years for incident diabetes, cardiovascular outcomes, kidney disease, and mortality. Results were published by Annals of Internal Medicine on June 19.
The study found 978 patients with elevated levels of fasting glucose or HbA1c at baseline, 39% with both (defined by the study authors as confirmed undiagnosed diabetes), and 61% with only one measure elevated (unconfirmed undiagnosed diabetes). Elevations on both measures had moderate sensitivity (54.9%) but high specificity (98.1%) for diagnosis of diabetes during the first five years of follow-up, with specificity increasing to 99.6% by 15 years. The 15-year positive predictive value was 88.7% for confirmed cases and 71.1% for unconfirmed cases. Participants with an elevation on either test had increased risk of cardiovascular and kidney disease and mortality during follow-up, but the association was stronger in the confirmed group than the unconfirmed.
The results “support the clinical utility of using a combination of elevated fasting glucose and HbA1c levels from a single blood sample to identify undiagnosed diabetes,” the authors said. They noted that this strategy would allow clinicians to make treatment decisions based on HbA1c level. Any significant discordance between the test results should be investigated, and patients with only one elevated test result should at least be followed, the authors said.
An accompanying editorial cautioned that the study population was black and white Americans ages 45 to 64 years and that the results may not be generalizable to other populations. Repeated measurements also find significantly more concordance between fasting glucose and HbA1c, suggesting that the single-sample strategy might miss many cases of diabetes, the editorial said. “This approach has appeal, especially for resource-challenged settings, but it needs replication in other populations before becoming accepted clinical practice,” it concluded.