Table 4.
Relationship between SOx and new-onset cardiovascular disease events by Cox proportional hazard analysis.
| Univariable analysis | Multivariable analysis | Variable selection (AIC) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| HR | 95%CI | P | HR | 95%CI | P | HR | 95%CI | P | |
| SOx ≥ 266.9 (µmol/L) | 2.79 | 1.26–6.16 | 0.011 | 1.92 | 0.79–4.68 | 0.150 | 2.10 | 0.90–4.91 | 0.086 |
| Age (years) | 1.02 | 0.99–1.06 | 0.159 | 1.00 | 0.96–1.04 | 0.951 | |||
| Male | 2.07 | 0.87–4.89 | 0.099 | 1.34 | 0.53–3.39 | 0.531 | |||
| HD duration (months) | 1.00 | 0.99–1.00 | 0.403 | ||||||
| History of CVD | 5.88 | 2.28–15.15 | < 0.001 | 3.23 | 1.06–9.85 | 0.039 | 3.84 | 1.44–10.2 | 0.007 |
| Diabetes mellitus | 1.41 | 0.65–3.07 | 0.390 | ||||||
| BMI (kg/m2) | 1.00 | 0.88–1.13 | 0.993 | ||||||
| Ankle-brachial index | 0.22 | 0.01–4.58 | 0.329 | ||||||
| aCa (mg/dL) | 0.58 | 0.24–1.39 | 0.221 | ||||||
| Phosphate (mg/dL) | 1.14 | 0.71–1.85 | 0.585 | ||||||
| iPTH (pg/dL) | 1.00 | 0.99–1.00 | 0.324 | ||||||
| ALP (IU/L) | 1.00 | 0.99–1.00 | 0.142 | 1.00 | 0.99–1.00 | 0.708 | |||
| Magnesium (mg/dL) | 0.44 | 0.13–1.55 | 0.201 | ||||||
| Triglyceride (mg/dL) | 1.00 | 1.00–1.01 | 0.306 | ||||||
| LDL-C (mg/dL) | 1.01 | 0.99–1.02 | 0.494 | ||||||
| HDL-C (mg/dL) | 0.96 | 0.93–1.00 | 0.030 | 0.97 | 0.94–1.00 | 0.091 | 0.97 | 0.94–1.00 | 0.062 |
| Uric acid (mg/dL) | 0.91 | 0.59–1.42 | 0.686 | ||||||
| β2MG (µg/L) | 0.99 | 0.93–1.06 | 0.837 | ||||||
| BUN (mg/dL) | 0.98 | 0.94–1.02 | 0.283 | ||||||
| Hemoglobin (g/dL) | 0.64 | 0.35–1.16 | 0.139 | 0.82 | 0.45–1.48 | 0.508 | |||
| Serum albumin (g/dL) | 0.53 | 0.13–2.11 | 0.367 | ||||||
| CaCO3 intake | 0.83 | 0.34–2.05 | 0.683 | ||||||
| Vitamin D medication | 1.33 | 0.63–2.81 | 0.451 | ||||||
| Statin intake | 1.03 | 0.39–2.73 | 0.952 | ||||||
We divided the subjects into two groups by SOx value ≥ 266.9 μmol/L and conducted a Cox proportional hazard analysis. The explanatory variable was SOx, and the covariates were factors that are reported to be associated with vascular calcification8,25,32,33 or CVD29,34–36. A univariable analysis was performed first, and factors with a two-tailed P value < 0.2 were used for a multivariable analysis. For variable selection, we used Akaike’s information criteria with stepwise backward elimination. A two-tailed P value of < 0.05 was considered to indicate statistical significance.
aCa albumin-adjusted calcium, AIC Akaike’s information criteria, ALP alkaline phosphatase, β2MG beta-2 microglobulin, BUN blood urea nitrogen, BMI body mass index, CaCO3 calcium carbonate, CI confidence interval, CVD cardiovascular disease, HD hemodialysis, HDL-C high-density lipoprotein cholesterol, HR hazard ratio, iPTH intact parathyroid hormone, LDL-C low-density lipoprotein cholesterol, SOx serum oxalate concentration.