Figure 1.

Proportion of the US population aged ≥12 years with an elevated filtration marker or CKD stage 3 by age. Elevated markers were β-trace protein (≥0.81 mg/L), β2-microglobulin (≥2.80 mg/L), standardized creatinine (men, ≥1.2 mg/dl; women, ≥1.0 mg/dl), or standardized cystatin C (≥1.03 mg/L). CKD stage 3 is defined as an estimated GFR <60 ml/min per 1.73 m², estimated using the Chronic Kidney Disease Epidemiology Collaboration equation (24). The elevated markers or CKD stage 3 are independent definitions determined solely by the markers themselves or the estimated GFR (eGFR).