Variables included | Models with Log(PCR) Transformed with a Five-Knot Restricted Cubic Spline | Models with Log(PCR) Transformed with a Four-Knot Linear Spline | Correlation Coefficient between Estimates from Model Pairs | ||||
---|---|---|---|---|---|---|---|

Model | No. of Coefficients | Pseudo R^{2} | Model | No. of Coefficients | Pseudo R^{2} | ||

Spline of log(PCR) only | C1 | 5 | 0.624 | L1 | 6 | 0.623 | >0.99 |

Spline of log(PCR), sex, and interactions | C2 | 10 | 0.629 | L2 | 12 | 0.628 | >0.99 |

Spline of log(PCR), sex, age, diabetes, hypertension and eGFR category, and interactions | C3 | 40 | 0.637 | L3 | 48 | 0.635 | >0.99 |

Spline of log(PCR) sex, age, diabetes, hypertension, eGFR category, laboratory location, and interactions | C4 | 50 | 0.642 | L4 | 60 | 0.641 | >0.99 |

The knots for the restricted cubic spline were at percentiles 5, 27.5, 50, 72.5, and 95 of log(PCR) (3.4668, 4.0625, 4.5664, 5.3992, and 7.7333, corresponding to PCR values of 32.0, 58.1, 96.2, 221, and 2283 mg/g). Knots for the linear spline were at values of log(PCR) of 3.689, 4.094, 5.521, and 6.908, corresponding to PCR values of 40, 60, 250, and 1000 mg/g. The number of coefficients includes the constant. The interactions are between the covariate and the spline terms. Pseudo

*R*^{2}is the proportion of the sum of absolute deviations from the median that is explained by the model.