Millions in United States May Have Undetected Chronic Kidney Disease

Nancy Fowler Larson

September 18, 2010

March 25, 2010 — As many as 13 million Americans may have undiagnosed diabetes or prediabetes and undetected chronic kidney disease (CKD), according to a study published in the April issue of the Clinical Journal of the American Society of Nephrology.

Available figures show that more than 40% of adults diagnosed with diabetes also have CKD, demonstrated by either albuminuria (excessive urine protein) or impaired kidney function. Diabetes affects 13% of adults, 25% of whom are undiagnosed. Thirty percent of adults have prediabetes, also called borderline diabetes.

"Despite the heavy burden of undiagnosed diabetes and prediabetes, relatively little is known about CKD prevalence in affected individuals," write Laura Plantinga, ScM, from the Department of Medicine, San Francisco General Hospital, and the University of California–San Francisco, and colleagues.

The study goal was to approximate the incidence of CKD in those with undiagnosed diabetes and prediabetes compared with others who have diagnosed diabetes or are free of the disease. Investigators used data from the 1999 through 2006 National Health and Nutrition Examination Survey to study nearly 8200 individuals. They evaluated factors including the demographics, socioeconomic status, and clinical indicators of the participants.

A "yes" answer to the question, "Have you ever been told by a doctor or other health professional that you have diabetes or sugar diabetes?" was the criteria for confirming a diagnosis. Subjects who answered "no" or "borderline" were sorted only by their fasting plasma glucose (FPG) measurement. FPG equal to or greater than 126 mg/dL was classified as undiagnosed diabetes, and FPG equal to or greater than 100 but less than 126 mg/dL was labeled as prediabetes. FPG of less than 100 mg/dL constituted no diabetes.

Because impaired kidney function can be present without albuminuria in those with type 2 diabetes, the researchers characterized CKD as the presence of reduced kidney function or albuminuria. An estimated glomerular filtration rate of 15 to 59 mL/minute/1.73 m2 or an albumin-creatinine ratio of more than 30 mg/g was used to designate CKD. Multivariable logistic regression was used to perform adjustments.

Findings Could Lead to New Diagnosis

The results showed nearly the same rate of CKD among those with diagnosed and undiagnosed diabetes, as follows:

  • 39.6% with diagnosed diabetes had CKD, as did 41.7% with undiagnosed diabetes

  • 17.7% with prediabetes and 10.6% without diabetes had CKD

  • 39.1% of participants with CKD had undiagnosed or prediabetes

"Based on these results, there may be a substantial number of individuals in the United States — up to 13 million — who have undiagnosed diabetes or prediabetes and who already have signs of kidney damage and/or reduced kidney function," Ms. Plantinga said in a news release. As explained in the news release, "Such patients would be at high risk for worsening kidney disease and diabetes, and for the poor outcomes associated with both conditions — including cardiovascular disease and death."

The prevalence of CKD after adjusting for age, sex, and race/ethnicity was 32.9%, 24.2%, 17.1%, and 11.8% for diagnosed, undiagnosed, prediabetes, and no diabetes, respectively. Subjects with undiagnosed diabetes were more often men than those with diagnosed diabetes (P = .005). Participants with prediabetes were more likely to be men than those with no diabetes (P < .001). Of those with undiagnosed diabetes, prediabetes, or no diabetes, most were non-Hispanic whites (P = .015, P < .001, and P < .001, respectively).

An editorial by Gary Curhan, MD, ScD, from the Channing Laboratory and Renal Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, published with the study, proposes a new diagnosis: pre-CKD. "The importance of prevention cannot be overstated," he said.

Dr. Curhan recommended that future studies establish a protocol for serial albuminuria and creatinine measurements for long-term tracking of alterations in albuminuria and kidney function. He added that it is critical to find out whether screenings should include those for serum phosphate and left ventricular hypertrophy — factors related to CKD.

"These data could lead to the development of risk scores, which would be particularly helpful in the clinical setting," Dr. Curhan said. "To make a substantial impact on this growing problem, we as a community need to focus on helping individuals avoid these preventable conditions."

The Centers for Disease Control and Prevention, in cooperation with the Association of American Medical Colleges, supported the study. The study authors have disclosed no relevant financial relationships.

Clin J Am Soc Nephrol. 2010;5:557-559, 673-682.

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