Early detection of undiagnosed non-insulin-dependent diabetes mellitus

Socio-economic status and undiagnosed diabetes

OBJECTIVE

To test the association of undiagnosed Type 2 diabetes mellitus with education and income level.

METHODS

We utilized measures of diabetes status, fasting plasma glucose, socio-economic status, and demographic characteristics from the National Health and Nutrition Examination Survey (NHANES III) for adults of age 20 and older. We inferred the presence of undiagnosed diabetes using the criterion of the American Diabetes Association at the time of NHANES III. A logistic regression analysis was used to examine the association of undiagnosed diabetes with education and income after controlling for other variables.

RESULTS

Undiagnosed diabetes is not related to education or income. In the sub-population of individuals with diagnosed or undiagnosed diabetes, undiagnosed diabetes is more likely in obese individuals (OR 1.95, 1.01-3.76), but is not related to education or income.

CONCLUSIONS

Socio-economic status, as measured by education and income, is not associated with whether or not individuals are likely to have undiagnosed diabetes. This finding suggests that screening for Type 2 diabetes should focus on those adults who are at risk for diabetes in general (based on age, racial/ethnic groups, obesity and other clinical risk factors) and that socio-economic characteristics are unlikely to provide further information.

Using HbA(1c) to improve efficacy of the american diabetes association fasting plasma glucose criterion in screening for new type 2 diabetes in American Indians: the strong heart study

OBJECTIVE

To find an optimal critical line in the fasting plasma glucose (FPG)-HbA(1c) plane for identifying diabetes in participants with impaired fasting glucose (IFG) and thereby improve the efficacy of using FPG alone in diabetes screening among American Indians.

RESEARCH DESIGN AND METHODS

We used FPG, 2-h postload glucose (2hPG), and HbA(1c) measured in the 2,389 American Indians (aged 45-74 years, without diabetes treatment or prior history of diabetes) in the Strong Heart Study (SHS) baseline (second) examination. Participants were classified as having diabetes if they had either FPG > or =126 mg/dl or 2hPG > or =200 mg/dl, as having IFG if they had 110 < or = FPG < 126 mg/dl, and as having normal fasting glucose (NFG) if they had FPG <110, according to the American Diabetes Association (ADA) definition. Logistic regression models were used for identifying diabetes (2hPG > or =200 mg/dl) in IFG participants. The areas under the receiver operating characteristic (ROC) curves generated by different logistic regression models were evaluated and compared to select the best model. A utility function based on the best model and the cost-to-benefit ratio was used to find the optimal critical line. The data from the second examination were used to study the effect of the time interval between the successive diabetes screenings on both the FPG criterion and the optimal critical line.

RESULTS

A total of 37% of all subjects with new diabetes at baseline and 55.2% of those in the second exam had 2hPG > or =200 but FPG <126. There was a very large portion of IFG participants with diabetes (19.3 and 22.9% in the baseline and second exam, respectively). Among the areas under the ROC curves, the area generated by the logistic regression model on FPG plus HbA(1c) is the largest and is significantly larger than that based on FPG (P = 0.0008). For a cost-to-benefit ratio of 0.23888, the optimal critical line that has the highest utility is: 0.89 x HbA(1c) + 0.11 x FPG = 17.92. Those IFG participants whose FPG and HbA(1c) were above or on the line were referred to take an oral glucose tolerance test (OGTT) to diagnose diabetes. The optimal critical line is lower if a successive diabetes screening will be conducted 4 years after the previous screening.

CONCLUSIONS

FPG > or =126 and 2hPG > or =200, as suggested by the ADA, are used independently to define diabetes. The FPG level is easy to obtain, and using FPG alone is suggested for diabetes screening. It is difficult to get physicians and patients to perform an OGTT to get a 2hPG level because of the many drawbacks of the OGTT, especially in those patients who already have FPG <126. It is also impractical to conduct an OGTT for everyone in a diabetes screening. Our data show that 37% of all subjects with new diabetes in the SHS baseline exam and 55.2% of those in the second exam have 2hPG > or =200 but FPG <126. These cases of diabetes cannot be detected if FPG is used alone in a diabetes screening. Therefore, although the small portion of diabetes in the NFG group (4.7% in the baseline and 6.9% in the second exam) may be ignored, those cases of diabetes among IFG participants ( approximately 20% in our data) need further consideration in a diabetes screening. It may be worthwhile for those IFG participants identified by the optimal critical line to take an OGTT. The optimal critical line and time interval between successive diabetes screenings need further study.

HbA1c measurement improves the detection of type 2 diabetes in high-risk individuals with nondiagnostic levels of fasting plasma glucose: the Early Diabetes Intervention Program (EDIP)

OBJECTIVE

Whereas new diagnostic criteria based on a fasting plasma glucose (FPG) of > 126 mg/dl (7.8 mmol/l) have improved the detection of diabetes, multiple reports indicate that many people with diabetes diagnosed by 2-h oral glucose tolerance test (OGTT) glucose measurements > or = 11.1 mmol/l (200 mg/dl) would remain undiagnosed based on this FPG criteria. Thus, improved methods to detect diabetes are particularly needed for high-risk individuals. We evaluated whether the combination of FPG and HbA1c measurements enhanced detection of diabetes in those individuals at risk for diabetes with nondiagnostic or minimally elevated FPG.

RESEARCH DESIGN AND METHODS

We analyzed FPG, OGTT, and HbA1c data from 244 subjects screened for participation in the Early Diabetes Intervention Program (EDIP).

RESULTS

Of 244 high-risk subjects studied by FPG measurements and OGTT, 24% of the individuals with FPG levels of 5.5-6.0 mmol/l (100-109 mg/dl) had OGTT-diagnosed diabetes, and nearly 50% of the individuals with FPG levels of 6.1-6.9 mmol/l (110-125 mg/dl) had OGTT-diagnosed diabetes. In the subjects with OGTT-diagnosed diabetes and FPG levels between 5.5 and 8.0 mmol/l, detection of an elevated HbA1c (>6.1% or mean + 2 SDs) led to a substantial improvement in diagnostic sensitivity over the FPG threshold of 7.0 mmol/l (61 vs. 45%, respectively, P = 0.002). Concordant FPG levels > or = 7.0 mmol/l (currently recommended for diagnosis) occurred in only 19% of our cohort with type 2 diabetes.

CONCLUSIONS

Diagnostic criteria based on FPG criteria are relatively insensitive in the detection of early type 2 diabetes in at-risk subjects. HbA1c measurement improves the sensitivity of screening in high-risk individuals.

Presence of diabetes related complication at the time of NIDDM diagnosis: an important prognostic factor

We studied the short-term natural history of patients with newly diagnosed non-insulin dependent diabetes mellitus (NIDDM), and the prognostic role of history of NIDDM related complication at the time of first NIDDM diagnosis in relation to the development of a new complication or death. We performed a cohort study using data from the General Practice Research Database in the UK. We identified patients aged 30 to 74 years with a newly diagnosed NIDDM between 1990 and 1992 and followed them from the day of NIDDM diagnosis until June 1995. Among the 1077 patients identified, 437 (41%) developed a NIDDM complication during the follow-up. NIDDM complications were more frequent among males and in the elderly. Sixty-seven percent of the study cohort was initially free of any complication while the remaining 360 patients presented already one or more NIDDM complication at the time of their NIDDM diagnosis. History of diabetic related complication was associated with an increased risk of developing a new NIDDM complication (RR: 1.8; 95% CI: 1.5-2.2). Mortality was also greater among patients with history of NIDDM complication (RR: 1.5; 95% CI: 1.0-2.2). Patients with a history of any disorder related to diabetes before their clinical diagnosis of NIDDM are at increased risk of developing a NIDDM complication after the NIDDM diagnosis, as well as at increased risk of dying compared to diabetic patients with no history.

Prevalence of diabetic retinopathy in an older community. The Blue Mountains Eye Study

OBJECTIVE

This study aimed to determine the prevalence and characteristics of diabetic retinopathy (DR) in a defined older Australian population.

DESIGN

A total of 3654 persons 49 years of age or older, 88% of permanent residents from an urban area west of Sydney, underwent a detailed eye examination. This included detailed medical history, Zeiss stereo retinal photography, fasting blood glucose, and other blood factors. The diagnosis of DR was made clinically and from photographic grading in persons with a history or biochemical evidence of diabetes.

RESULTS

Diabetes was present in 7% (95% confidence interval, 6.2-7.8) of the population. Signs of DR were found in 82 participants (2.3%; 95% confidence interval, 1.9-2.8). The prevalence was 1.7% in persons younger than 60 years of age, 2.4% in persons 60 to 69 years of age, 2.7% in persons 70 to 79 years of age, and 2.3% in persons 80 years of age or older. There was no significant gender difference in prevalence. After adjusting for age, gender, and the duration since diagnosis of diabetes, higher blood glucose was related to the finding of moderate-to-severe retinopathy (Wisconsin levels 4-7) compared to milder retinopathy (Wisconsin levels 1.5-3). No association was found between the presence of any retinopathy and blood glucose, a history of hypertension or elevated blood pressure, body-mass index, blood lipids, creatinine, or coagulation factors.

CONCLUSIONS

This Australian study has found similar prevalence rates for DR to a recent U.S. population-based study but lower rates for vision-threatening retinopathy than from clinic-based reports. Previous reports of a relationship between advanced retinopathy and blood glucose were supported. Other than diabetes duration and insulin treatment, no other associations with retinopathy were found.