NYU Langone Health Nov 7 2025 A mismatch between two common tests for kidney function may indicate a higher risk for kidney failure, heart disease, and death, a new study shows.  Health care providers for decades have measured blood levels of the molecule creatinine to track the rate at which kidneys filter waste from muscle breakdown in the bloodstream. According to more recent guidelines, levels of cystatin C, a small protein made by all cells in the body, can also be used to measure kidney