This story reported on a study that examined data from a long-running U.S. heart disease study to conclude that testing both a patient’s fasting glucose and A1C from a single blood sample is sufficient to confirm type 2 diabetes. Current guidelines call for performing either test once, followed by a second confirmatory test, thus requiring two separate lab visits and blood draws. The study was reported in the Annals of Internal Medicine.
The story’s strong point was that it tapped two independent sources. On the downside, it didn’t report that the single-sample testing method could miss many cases of diabetes or explore whether it would lead to better outcomes for patients, like avoiding complications of diabetes.
For help understanding medical tests such as these, see our primer: Understanding medical tests: sensitivity, specificity, and positive predictive value.
Testing for diabetes can help patients manage the disease before the onset of serious complications such as eye disease, kidney disease, heart disease, and stroke. Testing can also identify people at risk of developing type 2 diabetes, allowing them to make lifestyle changes such as losing weight.
Evidence supporting a simplified testing strategy — which is apparently already in use — might offer reassurance that the strategy is effective in identifying people who are likely to develop diabetes. On the other hand, it’s unclear from this study how much an impact this strategy would have on averting bad outcomes for patients.
The story provided no information on how much these tests cost. A check online found CVS drug store offered these tests for $59 apiece.
The story referred to the potential for a single test to result in quicker diagnosis and treatment of diabetes, thus “saving patients time and health care costs” and leading to better outcomes.
But it offered no data on how much more rapidly diagnosis and treatment might occur with single-sample testing, or more importantly how much difference it would make in heading off the many complications of diabetes.
According to the news release, 90% of those who tests positive in both tests went on to be diagnosed with diabetes within 15 years.
The story would have benefited from an exploration of the harms of overdiagnosis and overtreatment. Many of the patients who tested positive in both tests didn’t develop diabetes until a decade or two later. Potentially, patients like that could be treated overly aggressively with drugs that could do them harm.
Likewise, an accompanying editorial notes that the criteria proposed by the study might miss more people with diabetes than the conventional method of repeated blood glucose tests. In the data studied, simultaneous A1C and blood glucose tests agreed only about 40% of the time, versus 70% agreement for successive blood sugar tests.
Important caveats should have been mentioned, such as the study authors’ own acknowledgment that their findings need to be confirmed in other data sets.
The five-year intervals between blood glucose tests in the study population were much longer than what happens in clinical practice today, given screening recommendations for those at high risk.
As the editorial noted, the study included only black and white Americans aged 45 to 64 years, so the usefulness of these findings for other patient groups is uncertain.
There was no disease-mongering, but the story would have been stronger with information about who should be screened. For example, the U.S. Preventive Services Task Force recommends checking for abnormal blood glucose as part of cardiovascular risk assessment in adults who are overweight and between 40 and 70 years old, and referring those with abnormal levels to intensive behavioral counseling.
The story tapped independent diabetes experts.
While the study was funded by government grants, one of the authors disclosed grants and personal fees from industry, unrelated to the study.
The story made it clear that doing tests one at a time is called for in the current guideline.
But the story doesn’t mention the fasting plasma glucose test and the oral glucose tolerance test, which along with the glucose blood test, can be used if A1C test results aren’t consistent, the A1C test isn’t available, or you have a condition such as pregnancy that might render the A1C test inaccurate.
The story explained that both blood tests are routinely performed for diabetes.
The story explained that that some doctors already do conduct dual tests from a single blood sample, and that the study’s findings might support adding that strategy to clinical guidelines.
The story drew heavily from a Johns Hopkins news release but also used other sources.