Serum cystatin C and prediabetes in non-obese US adults.

Diabetes mellitus is the leading cause of end stage renal disease. Cystatin C, a marker of early renal impairment has been shown to be associated with diabetes. However, it is not clear if cystatin C is associated with prediabetes, an early stage in the hyperglycemic continuum where prevention efforts have been shown to be effective in delaying or preventing the onset of diabetes. We examined 2,033 participants from the National Health and Nutrition Examination Survey 1999-2002, aged ≥ 20 years (female 47.2 %) who were free of diabetes mellitus, chronic kidney disease and with body mass index <30 kg/m(2). Prediabetes (n = 541) was defined as a 2-h glucose concentration of 140-199 mg/dL, or a fasting glucose concentration of 110-125 mg/dL, or an A1C value of 5.7-6.4 %. Cystatin C levels were categorized into gender-specific quartiles for analysis. Elevated levels of serum cystatin C were associated with prediabetes after adjusting for potential confounders including serum total cholesterol, systolic blood pressure, body mass index and C-reactive protein. Compared to those with cystatin C in the lowest quartile, the multivariable odds ratio (95 % confidence interval) of prediabetes among those in the highest quartile was 2.08 (1.09-3.97), p for trend = 0.02. Although, this association was stronger among women and non-Hispanic whites, there was no significant interaction by sex (p = 0.1) or by race-ethnicity (p = 0.6). Our findings suggest that elevated levels of serum cystatin C are associated with prediabetes in a nationally representative sample of non-obese US adults.