1. Undiagnosed diabetes: Does limited access to healthcare explain high prevalence? Diane L. Manninen, Ph.D., Frederick B. Dong, A.M., and Carlyn E. Orians, M.A., Centers for Public Health Research and Evaluation, Battelle Memorial Institute, 4500 Sand Point Way, NE #100, Seattle, WA 98105-3949 Table 1 – Access and Use of Health Care by Diabetes Status § Using ADA CriteriaTable 2 – Prevalence of Undiagnosed Diabetes by Health Care Access and Utilization Table 3 – Prevalence of Undiagnosed Diabetes by Age, Health Insurance, and UtilizationTable 4 – Odds Ratio for the Likelihood of Undiagnosed Diabetes References 1.Harris MI, Flegal KM, Cowie CC, et. al. Prevalence of diabetes, impaired fasting glucose and impaired glucose tolerance in U.S. adults. Diabetes Care. 1998; 4:518-530. 2.Harris M. Undiagnosed NIDDM: clinical and public health issues. Diabetes Care. 1993; 16:642-652. 3.Harris MI, Modan M. Screening for NIDDM. Why is there no national program? Diabetes Care. 1994; 17:440-444. 4.Wei M, Haffner S, Stern M. High fasting glucose as a predictor of total and cardiovascular disease (CVD) mortality in patients with NIDDM [abstract]. Diabetes. 1997; 46(suppl 1):137A. 5.CDC Cost-Effectiveness Study Group. The cost-effectiveness of screening for Type 2 diabetes. JAMA. 1998; 280:1757-1763. 6.American Diabetes Association. Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus (Position Statement). Diabetes Care. 1999; 22(Suppl. 1): S5-19. 7.World Health Organization. Diabetes Mellitus: Report of WHO Study Group. Geneva, World Health Org. 1985 (Tech Rep. Ser. No. 727). 8.Stata Corporation. Stata Statistical Software: Release 7.0. College Station, Texas. 2001. 9.Nichols GA, Glauber HS, Brown JB. Type 2 diabetes: incremental medical care costs during the 8 years preceding diagnosis. Diabetes Care. 2000 Nov;23(11):1654-9. 10.Levetan CS, Passaro M, Jablonski K, Kass M, Ratner RE. Unrecognized diabetes among hospitalized patients. Diabetes Care. 1998; 21:246-249. 11.Peters AL, Davidson MB, Schriger L, Hasselblad V. A clinical approach for the diagnosis of diabetes mellitus. JAMA. 1996; 276(15):1246-1262. Background Objective Type 2 diabetes is a common and serious disease in the United States.  Approximately 12.3% of U.S residents between the ages of 40 and 74 have diabetes—one-third of which has not been diagnosed. The prevalence of diabetes (both diagnosed and undiagnosed) has been increasing. 1 Prevalence of diabetes varies by age and race/ethnicity. 1  Undiagnosed diabetes is not a benign condition. Diabetes is associated with a number of microvascular complications (e.g., retinopathy, neuropathy, nephropathy) and individuals with diabetes are at an increased risk for blindness and renal failure. Among individuals who are diagnosed with Type 2 diabetes, 20% have background retinopathy and 10.5 % have nephropathy present at the time of clinical diagnosis. 2-4  Early detection of diabetes can lead to earlier treatment through improved glycemic control. Better glycemic control can reduce the incidence and slow the progression of microvascular complications. 5  An opportunistic screening program for diabetes is cost- effective. 5 However, an opportunistic screening program requires access to health care and the utilization of health care services. The objectives of the study were:  To compare the prevalence of undiagnosed diabetes by measures of health care access and utilization; and  To estimate the risk of undiagnosed diabetes by measures of health care access and utilization. Conclusions ADA Criterion Figure 1. Odds Ratio for Undiagnosed Diabetes by Race/Ethnicity and Access/Utilization of Health CareMethods Undiagnosed Diabetes Undiagnosed diabetes was determined based upon the results of a fasting plasma glucose test.  Health insurance (Medicare, Medicaid, Champus, or private health insurance).  A particular place for care.  A particular doctor for care.  Seen a doctor in the past year.  Seen a doctor two or more times in the past year.  Been hospitalized in the past year. Health Care Access and Utilization Measures Data Sources The prevalence of undiagnosed diabetes was estimated using data from the Third National Health and Nutrition Examination Survey (NHANES III), a nationally representative sample of the non- institutionalized U.S. population. The NHANES III sample included 18,825 adults ages 20 and over.  Socioeconomic and demographic data were obtained from the NHANES III household file and clinical blood chemistry values were obtained from the NHANES III laboratory file.  Those with previously diagnosed diabetes were excluded from the analysis (n=1,500), unless diabetes was diagnosed only during pregnancy.  Individuals were excluded if they did not have valid test results for determining diabetes status.  A total of 6,029 individuals were included in the analysis  Only those individuals who received their examination in the morning and fasted during the previous 9 to 24 hours (n=5917).  Applying criteria established by the American Diabetes Association (ADA), individuals with a fasting plasma glucose (FPG) of 126 mg/dl or more were considered to have undiagnosed diabetes (n=231). 6 World Health Organization (WHO) criteria 7 were considered as an alternative definition of diabetes. Several measures of health care access and utilization were constructed from Health Insurance and Health Services sections of the NHANES III survey. These included dichotomous variables indicating whether the individual had: Statistical Methods  Stata statistical software 8 was used to account for clustered sample design and sample weights.  Two-sample t-tests were used to compare health care access and utilization measures of individuals with undiagnosed diabetes and those without diabetes.  Multivariate logit analysis was used to estimate the risk of undiagnosed diabetes by measures of health care access and utilization.Results  As shown in Table 1, those with undiagnosed diabetes were more likely to have a particular place for health care and were more likely to have utilized health care services (e.g., had seen a doctor, had been hospitalized) in the past year compared with those without diabetes.  Prevalence of undiagnosed diabetes is as high or higher among those who have access to and/or utilize the health care system compared to those who do not. As shown in Table 2, the prevalence of undiagnosed diabetes was 3.04% for people with a particular place for care versus 1.15% for those without. Prevalence of undiagnosed diabetes was higher for those who had seen a doctor in the past year, had seen a doctor two or more times in the past year or had been hospitalized.  The prevalence of undiagnosed diabetes increases with age. As shown in Table 3, the relationship between the prevalence of undiagnosed diabetes by age and health care access and utilization is mixed and generally not significant. People with undiagnosed diabetes have equal or better access to health care services compared with people without diabetes. The prevalence of undiagnosed diabetes does not appear to be higher among those with limited access to and/or utilization of health care services, even after controlling for age and race/ethnicity.  Age and race/ethnicity are important risk factors for undiagnosed diabetes. As shown in Table 4, controlling for differences by age and race/ethnicity, individuals who had a regular place for health care were more likely to have undiagnosed diabetes compared with individuals without a regular place of care. Similarly, individuals who had been hospitalized in the past year were more likely to have undiagnosed diabetes compared to individuals who had not been hospitalized.  Since health care access and/or utilization vary by race/ethnicity, we added interaction terms to the analysis to examine whether this affects the relationship between undiagnosed diabetes and health care access. For all three racial/ethnic groups, there is little evidence of a relationship between health care access and utilization and the likelihood of undiagnosed diabetes (see Figure 1). In most cases racial/ethnic minorities with access to health care are more likely to have undiagnosed diabetes compared with individuals with poorer access to care. Results of analysis using World Health Organization definition of diabetes were similar to the results using the ADA criteria. Limited access to health care services does not explain observed differences in undiagnosed diabetes. Rather, the prevalence of undiagnosed diabetes is as high or higher among those with better access and higher utilization than among those for whom access and utilization are lower.  Even after controlling for age and race/ethnicity, the prevalence of undiagnosed diabetes is as high or higher among individuals with health care access compared with individuals whose access to health care is more limited.  People who utilize the health care system—in particular among those who were hospitalized—are more likely to have undiagnosed diabetes.  Higher utilization of health care services among people with undiagnosed diabetes is consistent with previous studies that have observed that higher utilization occurs eight years preceding diagnosis. 9 Therefore, there appears to be ample opportunity for improvements in health outcomes, in a cost-effective manner, through “opportunistic” screening for Type 2 diabetes. Failure to screen and diagnose people with diabetes may be due to other factors.  The fasting plasma glucose test may be inconvenient. The test is only valid if the patient has not eaten.  Test results are often ignored. One-third of patients receiving surgical or medical services who were found to be hyperglycemic had no mention of diabetes in their medical records. 10  Other tests for diabetes—for example, a glycosylated hemoglobin (HbA 1c ) test, which is less sensitive to both food intake and physical activity levels 11 — may be useful. **