Mean regression lines and 95% limits of agreement for A) Estimated 24-hour creatinine excretion (eCER) and B) spot urine creatinine (UCr) with fat free mass (FFM) by dual x-ray absorptiometry (DXA) in Men (n=573) in gray triangles and Women (n=798) in black circles
A) Regression equation: Men FFM (kg) = 4.3 + 0.04*CER (mg/day); Women FFM = 21.0 + 0.02*CER (mg/day)
B) Regression equation: Men FFM (kg) = 54.3 + 0.03* spot UCr (mg/dL); Women FFM (kg) = 37.9 + 0.015* spot UCr (mg/dL)