Table 3.

Hemoglobin (g/dl) versus GFR (ml/min per 1.73 m2) and covariates in a threshold regression model

ParameterParameter Estimates (95% CI)
Unadjusted(n = 340)Age/Gender Adjusted(n = 340)Fully Adjusted(n = 339)
GFR threshold, c (ml/min per 1.73 m2)43 (28 to 52)43 (29 to 51)43 (NA)a
Y-intercept, mean hemoglobin at GFR threshold, c (g/dl)12.6 (12.3 to 12.9)12.6 (12.3 to 13.0)12.7 (12.5 to 13.1)
Parameter
GFR ≤c, per 5-ml/min per 1.73 m2 decrease−0.3 (−0.5 to −0.2)−0.4 (−0.5 to −0.2)−0.3 (−0.5 to −0.2)
GFR >c, per 5-ml/min per 1.73 m2 decrease−0.1 (−0.2 to 0.0)−0.1 (−0.2 to 0.0)−0.1 (−0.2 to 0.0)
Female gender−0.1 (−0.5 to 0.2)0.0 (−0.4 to 0.3)
Age, per 5-yr increase0.1 (−0.1 to 0.3)0.2 (0.0 to 0.4)
Black versus nonblack race−0.1 (−0.6 to 0.3)
Glomerular versus nonglomerular CKD−0.9 (−1.3 to −0.5)
  • a 95% CI was not attainable (NA): The lower bound was less than a GFR of 20 ml/min per 1.73 m2, and the upper bound was >60 ml/min per 1.73 m2, the bounds of the search for threshold, c, using profile likelihood.