Comparison of Serum Concentrations of β-Trace Protein, β2-Microglobulin, Cystatin C, and Creatinine in the US Population

Background and objectives beta-trace protein (beta TP), beta 2-microglobulin (beta 2M), and cystatin C (CysC) have advantages over creatinine for estimating GFR and prognosis. This study compares the distribution of all four markers in the general population and their associations with possible determinants of GFR. Design, setting, participants, & measurements beta TP and beta 2M were measured in 7596 participants (aged >= 12 years) of the Third National Health and Nutrition Examination Survey (1988-1994). beta TP and beta 2M concentrations and the proportion of persons with elevated (>= 99th percentile for young healthy participants) beta TP (>= 0.81 mg/L), beta 2M (>= 2.80 mg/L), standardized CysC (>= 1.03 mg/L), and creatinine (>= 1.2 mg/dl for men and >= 1.0 mg/dl for women) were compared across demographic and clinical factors. Results Elevated beta TP, beta 2M, and CysC showed stronger associations with age than elevated serum creatinine, the prevalence of elevated levels reaching 47%, 44%, 58%, and 26%, respectively, by age 80 years. beta TP, CysC, and creatinine were higher in men but beta 2M was not associated with sex. Mexican Americans had lower beta TP, beta 2M, CysC, and creatinine compared with non-Hispanic whites. Hypertension and higher C-reactive protein were associated with elevations in all markers, whereas non-Hispanic black race, body mass index, diabetes, smoking status, triglycerides, HDL cholesterol, and education were not associated in a consistent manner across the different markers. Conclusions beta TP, beta 2M, CysC, and creatinine differ in their associations with demographic and clinical factors, suggesting variation in their non-GFR determinants. Future studies should examine these markers with measured GFR to determine their diagnostic and prognostic utility. Clin J Am Soc Nephrol 8: 584-592, 2013. doi: 10.2215/CJN.08700812