Purpose: Nearly one third of diabetes cases in the United States is undiagnosed, with mounting evidence that complications accrue even before clinical diagnosis. We wanted to determine whether persons with undiagnosed diabetes have signs of nephropathy and peripheral neuropathy.
Methods: We examined the prevalence of positive screening tests for nephropathy and peripheral neuropathy in adults aged > or = 40 years with undiagnosed diabetes using secondary analysis of survey and examination data from the population-based United States National Health and Nutrition Examination Survey 1999-2002. We defined a positive screening test for nephropathy as a spot urine albumin-creatinine ratio > 30.0 mg/g, representing at least microalbuminuria. We defined > or = 1 insensate area on Semmes-Weinstein monofilament testing as a positive finding for neuropathy. Undiagnosed diabetes was defined as a combination of no history of diagnosed diabetes and a measured fasting glucose > or = 126 mg/dL. We used SUDAAN for chi2 and regression analyses.
Results: The prevalence of a positive test when screening for nephropathy among those with undiagnosed diabetes was 26.5% compared with 7.1% in those with no diabetes (chi2, P <.01). After adjusting for age and diagnosed or undiagnosed hypertension, the association of undiagnosed diabetes with nephropathy persisted (odds ratio = 2.35; 95% confidence interval, 1.38-4.01). For peripheral neuropathy, 21.5% with undiagnosed diabetes had positive screening tests compared with 10.1% with no diabetes (chi2, P <.01); however, this effect was not significant after adjustment for age. There was no significant difference in positive screening tests for nephropathy or neuropathy when comparing those with undiagnosed and diagnosed diabetes.
Conclusions: A significant proportion of adults with undiagnosed diabetes have signs of nephropathy and peripheral neuropathy. These findings may influence policies about early screening for diabetes.