In this retrospective study, 2320 PD patients were screened while 918 patients were excluded. Among the patients excluded, 269 patients were followed up for less than 6 months, 263 patients were converted to hemodialysis treatment, 97 patients had no key clinical information, 264 patients had no complete data of research indicators, and 25 patients were under 18 years old. A total of 1402 patients were included. There were 763 males (54.42%) and 639 females (45.58%). Their average age at the start of PD was 49.50 ± 14.20 years old. There were 317 (22.61%) patients received renal transplantation and 22 (1.57%) patients lost follow-up.
The trend of SUA level during PD follow up was shown in Fig. 1. The SUA levels were 7.97 ± 1.79 mg/dl at baseline, 7.12 ± 1.48 mg/dl at 6 months, 7.05 ± 1.33 mg/dl at 12 months, 7.01 ± 1.30 mg/dl at 18 months, and 6.93 ± 1.26 mg/dl at 24 months. There were significant differences in SUA between baseline and each follow up time (6, 12, 18 or 24 months of PD) (P < 0.01),and there was statistical difference between 6 months and 24 months (P < 0.01).
During median follow-up time of 31 (18, 49) months, 173 (12.34%) all-cause deaths occurred, including 68 (4.85%) cardiovascular deaths. The characteristics of the patients with all-cause deaths and cardiovascular deaths were shown in Table 1. The values of age, SUA at 6 months, serum glucose and CCI were higher in patients with all-cause deaths than the other patients; while the values of follow-up time, baseline SUA, DBP, and serum levels of creatinine, phosphorus and albumin were lower in patients with all-cause deaths than the other patients. The values of age, SBP, CCI, and serum levels of triglyceride and glucose were higher in patients with cardiovascular deaths than the other patients; while the values of follow-up time, baseline SUA, serum levels of creatinine and albumin were lower in patients with cardiovascular deaths than the other patients.
Table 1
Clinical characteristics according to groups by prognosis.
Variants | Total (n = 1402) | Grouped by all-cause death | Grouped by cardiovascular death |
All-cause death(173) | Other(1229) | P value | Cardiovascular death(68) | Other(1334) | P value |
Follow-up duration (m) | 36.11 ± 23.26 | 30.82 ± 18.04 | 36.85 ± 23.81 | 0.001 | 30.35 ± 19.47 | 36.40 ± 23.40 | 0.036 |
Male (N, %) | 763(54.42) | 90(52.0) | 673(54.76) | 0.499 | 42(61.76) | 721(54.05) | 0.213 |
Age (y) | 49.50 ± 14.20 | 61.27 ± 13.24 | 47.84 ± 13.53 | < 0.001 | 58.57 ± 13.36 | 49.04 ± 14.09 | < 0.001 |
SUA (baseline)༈mg/dl༉ | 7.97 ± 1.79 | 7.65 ± 1.91 | 8.01 ± 1.77 | 0.014 | 7.52 ± 1.66 | 7.99 ± 1.79 | 0.034 |
SUA(PD 6m)༈mg/dl༉ | 7.12 ± 1.48 | 7.38 ± 1.81 | 7.08 ± 1.43 | 0.015 | 7.30 ± 1.91 | 7.11 ± 1.46 | 0.303 |
SUA(PD 12m)༈mg/dl༉ | 7.05 ± 1.33 | 7.11 ± 1.43 | 7.04 ± 1.32 | 0.569 | 6.98 ± 1.18 | 7.06 ± 1.34 | 0.678 |
SUA(PD 18m)༈mg/dl༉ | 7.01 ± 1.30 | 7.15 ± 1.33 | 6.99 ± 1.30 | 0.186 | 7.03 ± 1.23 | 7.01 ± 1.31 | 0.932 |
SUA(PD 24m)༈mg/dl༉ | 6.93 ± 1.26 | 6.96 ± 1.47 | 6.93 ± 1.24 | 0.792 | 7.10 ± 1.43 | 6.93 ± 1.26 | 0.400 |
BMI (kg/m2) | 21.52 ± 3.26 | 21.63 ± 3.51 | 21.50 ± 3.22 | 0.633 | 22.27 ± 3.16 | 21.48 ± 3.26 | 0.051 |
Serum creatinine(mg/dl) | 8.54 ± 3.16 | 7.66 ± 3.02 | 8.67 ± 3.16 | < 0.001 | 7.62 ± 2.54 | 8.59 ± 3.18 | 0.014 |
Potassium (mmol/L) | 4.54 ± 0.70 | 4.51 ± 0.71 | 4.54 ± 0.70 | 0.590 | 4.50 ± 0.70 | 4.54 ± 0.70 | 0.645 |
Calcium (mmol/L) | 2.08 ± 0.25 | 2.10 ± 0.23 | 2.08 ± 0.26 | 0.504 | 2.11 ± 0.22 | 2.08 ± 0.25 | 0.467 |
Phosphorus (mmol/L) | 1.82 ± 0.49 | 1.72 ± 0.54 | 1.83 ± 0.26 | 0.007 | 1.74 ± 0.48 | 1.82 ± 0.49 | 0.191 |
Albumin (g/L) | 36.92 ± 5.32 | 35.29 ± 5.23 | 37.15 ± 5.30 | < 0.001 | 35.36 ± 5.51 | 37.00 ± 5.30 | 0.013 |
Triglyceride(mmol/L) | 1.54 ± 0.97 | 1.65 ± 1.02 | 1.53 ± 0.97 | 0.139 | 1.80 ± 1.24 | 1.53 ± 0.96 | 0.027 |
TC(mmol/L) | 4.31 ± 1.19 | 4.42 ± 1.34 | 4.29 ± 1.17 | 0.172 | 4.11 ± 1.36 | 4.30 ± 1.18 | 0.327 |
HDL-C(mmol/L) | 1.11 ± 0.35 | 1.09 ± 0.37 | 1.11 ± 0.35 | 0.42 | 1.05 ± 0.33 | 1.11 ± 0.35 | 0.18 |
LDL-C(mmol/L) | 2.38 ± 0.87 | 2.44 ± 0.98 | 2.37 ± 0.85 | 0.307 | 2.45 ± 1.00 | 2.37 ± 0.86 | 0.477 |
AKP(U/L) | 78.52 ± 52.85 | 82.74 ± 58.11 | 77.92 ± 52.07 | 0.262 | 79.49 ± 29.89 | 78.48 ± 53.77 | 0.876 |
Glucose(mmol/L) | 4.82 ± 1.20 | 5.33 ± 2.00 | 4.74 ± 1.03 | < 0.001 | 5.60 ± 2.60 | 4.77 ± 1.07 | < 0.001 |
CRP(mg/L) | 9.75(2.5,9.75) | 2.30(1.50,7.53) | 2.90(1.50,7.70) | 0.588 | 2.80(1.80,9.20) | 9.75(2.5,9.75) | 0.918 |
Hemoglobin (g/L) | 83.49 ± 16.74 | 82.19 ± 17.59 | 83.67 ± 16.62 | 0.274 | 83.36 ± 19.35 | 83.50 ± 16.61 | 0.946 |
iPTH (pg/mL) | 285.00(151.75,454.00) | 224.00(128.98,365.75) | 288.50(155.00,467.50) | 0.089 | 203.00(108.00,330.50) | 290.00(154.00,456.50) | 0.050 |
SBP(mmHg) | 146.57 ± 20.59 | 148.43 ± 25.54 | 146.31 ± 19.80 | 0.203 | 151.40 ± 25.48 | 146.32 ± 20.29 | 0.047 |
DBP(mmHg) | 88.76 ± 14.09 | 85.23 ± 15.43 | 89.26 ± 13.82 | < 0.001 | 87.18 ± 15.86 | 88.85 ± 14.00 | 0.342 |
Ccr (ml×week/min/ /1.73 m2 ) | 52.24 ± 36.31 | 50.57 ± 36.15 | 52.48 ± 34.68 | 0.502 | 55.03 ± 38.81 | 52.11 ± 34.65 | 0.507 |
CCI | 2.51 ± 0.94 | 2.97 ± 1.24 | 2.44 ± 0.87 | < 0.001 | 3.06 ± 1.13 | 2.48 ± 0.92 | < 0.001 |
We graded SUA levels at baseline, 6 months, 12 months, 18 months and 24 months during follow-up by mean of SUA plus or minus a standard deviation as cut-off values. Kaplan-Meier survival analysis and Cox regression analysis showed that there were no significant differences on all-cause mortality among groups with graded SUA levels at baseline, 12 months, 18 months and 24 months during follow-up (Fig. 2, ACDE; Table 2),or on cardiovascular mortality among groups with graded SUA levels at baseline, 6 months, 12 months, 18 months and 24 months during follow-up (data not shown).
Table 2
Multivariate Cox regression analysis of follow-up SUA levels and all-cause mortality.
| Baseline | | 6 months | | 12 months | | 18 months | | 24 months | |
| HR(95%CI) | P | HR(95%CI) | P | HR(95%CI) | P | HR(95%CI) | P | HR(95%CI) | P |
Grade1 | 0.972(0.649–1.454) | 0.889 | 1.428(0.886–2.302) | 0.143 | 0.932(0.545–1.595) | 0.798 | 0.500(0.235–1.064) | 0.072 | 0.678(0.367–1.251) | 0.214 |
Grade2 | reference | reference | reference | reference | reference |
Grade3 | 0.784(0.536–1.145) | 0.207 | 1.524(1.046–2.219) | 0.028 | 1.000(0.684–1.461) | 0.999 | 0.907(0.597–1.376) | 0.646 | 0.543(0.337–0.875) | 0.012 |
Grade4 | 0.806(0.484–1.340) | 0.406 | 1.824(1.181–2.817) | 0.007 | 1.287(0.793–2.089) | 0.307 | 0.903(0.531–1.535) | 0.705 | 0.979(0.566–1.694) | 0.939 |
Note: Reference group is Grade2 group. Multivariate Cox regression analysis was performed at baseline, 6 months, 12 months, 18 months and 24 months. The factors adjusted included age, serum creatinine, serum phosphorus, serum albumin, serum glucose, DBP and CCI. |
For SUA at 6 months of PD, we graded the PD patients into Grade 1 (SUA < 5.65 mg/dl), Grade 2 (5.65 mg/dl ≤ SUA < 7.13 mg/dl), Grade3 (7.13 mg/dl ≤ SUA ≤ 8.61 mg/dl) and Grade4 (SUA > 8.61 mg/dl) according to mean of SUA plus or minus a standard deviation as cut-off values. Kaplan Meier analysis showed that there was significant difference on all-cause mortality among the above Grades (χ2 = 11.315, P = 0.010) (Fig. 2B). The all-cause mortality tended to be lowest in Grade 2, and significantly lower in Grade 2 than those in Grade 3 and Grade 4 (HR = 2.219, P = 0.028; HR = 2.817, P = 0.007, respectively) (Table 2).
For SUA at 24 months of PD, we graded the PD patients into Grade 1 (SUA < 5.68 mg/dl), Grade 2 (5.68 mg/dl ≤ SUA < 6.94 mg/dl), Grade 3 (6.94 mg/dl ≤ SUA ≤ 8.20) and Grade 4 (SUA > 8.20 mg/dl) according to mean of SUA plus or minus a standard deviation as cut-off values. Kaplan Meier analysis showed that there was no significant difference in all-cause survival rates among the above groups (χ2 = 6.145, P = 0.105) (Fig. 2E). However, the all-cause mortality tended to be lowest in grade 3, and significantly lower in Grade 3 than that in Grade 2 (HR = 0.543, P = 0.012) (Table 2).