Table 4. Multivariable Cox proportional hazard analysis for the association of IS and pCS serum levels with renal survival.

	AIC	Parameter	Estimate	Standard Error	p-value	Hazard Ratio	95% Hazard Ratio Confidence Intervall
Model 0 total cohort	3412.5	---				---	---	---
Model 1a	3412.2	Log IS	0.07	0.04	0.131	1.07	0.98	1.17
Model 1b	3400.3	Q2: 2.9–5.3	0.15	0.18	0.426	1.16	0.80	1.65
		Q3: 5.3–11.6	-0.15	0.19	0.422	0.86	0.59	1.25
		Q4: >11.6	0.48	0.19	0.011	1.62	1.12	2.35
Model 1c	3414.1	Log pCS	-0.037	0.06	0.533	0.96	0.86	1.08
Model 1d	3416.7	Q2: 7.9–17.2	-0.22	0.17	0.201	0.80	0.57	1.12
		Q3: 17.2–29.6	-0.17	0.18	0.317	0.84	0.60	1.18
		Q4: >29.6	-0.13	0.18	0.464	0.88	0.61	1.25
Model 0 consolidated cohort	3088.5	---				---	---	---
Model 1e	3083.9	Log IS	0.20	0.08	0.001	1.23	1.05	1.43
Model 1f	3072.4	Q2: 2.9–5.3	0.17	0.18	0.371	1.18	0.82	1.69
		Q3: 5.3–11.6	-0.10	0.20	0.600	0.90	0.62	1.32
		Q4: >11.6	0.66	0.21	0.002	1.94	1.29	2.93

Model 0 represents a Cox model with sex, age, diagnosis, region of residence, body mass index SDS, blood pressure SDS, estimated glomerular filtration rate, urinary protein creatinine ratio, hemoglobin, serum phosphorus and albumin as covariates, calculated either for the total cohort (n = 569) or for the consolidated cohort (excluding patients with IS levels exceeding the 95% upper prediction limit, n = 526). Model 1a includes serum IS, 1b IS quartiles, 1c serum pCS and 1d serum pCS quartiles as a covariate to model 0. Models 1e and 1 f include serum IS and serum IS quartiles respectively as covariates to model 0 in the consolidated cohort. IS and pCS are used as logarithmic values in all models. For all variables associated with renal survival (model 0, total cohort) please refer to Table 3. IS = indoxyl sulfate; pCS = p-cresyl sulfate; Q = quartiles of serum IS and pCS levels, respectively; AIC = Akaike information criterion.